Shunting normal-pressure hydrocephalus: Do the benefits outweigh the risks? A multicenter study and literature review J. Vanneste, MD; P. Augustijn, MD; C. Dirven, MD; W.F. Tan, MD; and Z.D. Goedhart, MD
Article abstract-We performed a multicenter retrospective study in 166 consecutive patients shunted for presumed normal-pressure hydrocephalus (NPH) in the four neurosurgical departments of Amsterdam. Overall improvement occurred in 36%, substantial improvement in 21%. In the subgroup of idiopathic NPH (N = 127), marked improvement was only 15%. The incidence of shunt-responsive NPH in our area was 2.2/million/year. The rate of severe and moderate shunt-related complications was 28%, leading to death or severe residual morbidity in 7%. The substantial benefit/serious harm ratio in the whole group was only three (21%/7%), decreasing to 1.7 in idiopathic NPH. By excluding patients at high surgical risk, this ratio might have risen to 10 in the whole group and to six in idiopathic NPH. Our experience is much less favorable than that encountered in the literature, reporting overall improvement in 74% and marked improvement in 55% of the shunted patients. We conclude that NPH is probably a very rare and still overdiagnosed syndrome and that the overall morbidity rate for each patient demonstrating meaningful improvement is high. NEUROLOGY 1992;42:54-59
between the benefits and the surgical risks, we carGait disturbances, mental impairment, and uriried out this study to answer three questions: nary urgency o r incontinence associated with 1. A clinical study: What are the benefit and hydrocephalus and normal pressure at lumbar puncture may be reversed by CSF d i ~ e r s i 0 n . l . ~ complication rates calculated from the results of a retrospective multicenter study on all patients Twenty-five years after the first description of the shunted for presumed NPH? syndrome of normal-pressure hydrocephalus 2. A literature study: What is the expected rate (NPH), the therapeutic approach remains problemof improvement and complications in shunted NPH atic. Clinicians still waver between the fear of patients when the data from the appropriate literamissing a treatable dementia or gait disorder and ture published between 1966 and 1990 are pooled? the reluctance to submit their presumed NPH 3. A comparison of studies 1 and 2 (above): What patients to the risks of ventricular drainage. are the similarities and discrepancies and the conManagement is based mainly on articles providsequences for clinical practice? ing data on percentages of benefit*-22and shuntThe varirelated complications (SRC).4,6-9,12-16,19,23-31 Methods. Clinical study. Patients. All neurosurgical and ability of clinical response is considerable: mean neurologic charts, available CTs, and cisternograms of rates of improvement average 50%,9,22,31 with wide 166 consecutive patients with a n admission diagnosis of SRC occur in 30 t o variations from 25 to 80%.6J8,32,33 NPH, shunted between January 1980 and July 1989 in 40% of patients, but comments on complications the four neurosurgical departments of Amsterdam, were vary from reassuring remarks on the reversibility reviewed. The departments consist of two university of most complications8J4J6t o alarming comments departments of neurosurgery and two neurosurgical seron the frequency of shunt-related disaster^.^^^^^ The vices in teaching hospitals-together the referral neurovariability of clinical details on complications, more surgical centers for a population of about 2.5 million peoparticularly their impact on residual morbidity, ple. To clarify uncertainties on clinical outcome, we also reviewed the notes of the nursing staff and contacted by may have contributed to these divergent estimatelephone some patients, their family, or the general tiorm31 practitioner. We considered the diagnosis of NPH if the As controversy persists regarding t h e ratio
From the Department of Neurology (J. Vanneste, P. Augustijn), St. Lucasziekenhuis; the Department of Neurosurgery (C. Dirvenj, Academic Hospital, Free University of Amsterdam; the Department of Neurosurgery (W.F. Tan), Academic Medical Centre, University of Amsterdam; and the Department of Neurosurgery (Z.D. Goedhart), Municipal Hospital Slotervaart, Amsterdam, The Netherlands. Received March 6, 1991. Accepted for publication in final form June 17, 1991 Address correspondence and reprint requests to Dr. J. Vanneste, Department of Neurology, St. Lucasziekenhuis 164, 1061 AE Amsterdam, The Netherlands. 54 NEUROLOGY 42 January 1992
clinical and CT criteria were met as has been previously des~ribed.~,~.~~.~~ Clinical characteristics. As far as possible, gait disturbances were graded on an ordinal scale with five categories: normal (0); unstable, but still independent gait (la), or small-stepped, independent gait ( l b ) ; walking with some aid (eg, cane) ( 2 ) ; walking with substantial aid (eg, two canes or a walker) ( 3 ) ; and walking not possible, wheelchair-bound (4).Mental impairment was divided into four categories: no apparent dementia (O), mild mental slowness and memory disturbances ( l ) , moderately severe mental impairment (21, and severe dementia (3). When cognitive impairment included cortical dysfunction such as aphasia, apraxia and agnosia, it was separately recorded. Bladder disturbances were ranked into three categories: absent (0), increased urinary frequency (l), and incontinence (2). When expression in one category was not possible on the basis of available data, two contiguous categories were used, eg, gait 213. The general condition and the presence of diseases considered to increase the surgical risks were noted. As this is a retrospective study, we could not find sufficient details to quantify t h e risks of anesthesia or neurosurgery. Despite this, we estimated that patients were at high surgical risks when they had a combination of three of the following variables: cardiac dysrhythmia, a history of recent myocardial infarction, pulmonary obstructive disease requiring medication, a history of one or more major strokes, and other rare conditions such as a histor y of recurrent lung embolisms requiring anticoagulant therapy. Improvement. Improvement was rated as follows: no effect (0); some improvement ( + l ) , when gait disturbance, mental impairment, or both ameliorated 1 point on the ordinal scale, or when the patient, his or her family, and t h e neurologist agreed t h a t there was slight improvement, but less than 1grade on the ordinal scales, eg, a n unstable, independent gait (grade 1)becoming less unstable after shunting. Marked improvement (+2) implied that gait, mental disturbances, or both ameliorated 2 points or more on the ordinal scale, or when the patient, the nurses, and the neurologist estimated that shunting had been followed by a substantial clinical improvement. All improvements had to be confirmed by two independent assessors. Duration of improvement was also registered; it was considered as definitive either in patients whose improvement persisted until the last follow-up (but at least for 1year), or in patients who died earlier or were incapacitated by unrelated causes but had remained improved for at least 6 months. When improvement was followed by relapse t h a t did not respond to shunt revisions or other therapeutic meas u r e s , it was categorized s e p a r a t e l y as t e m p o r a r y improvement (TI), even when NPH recurred after 1year or longer. As not all patients were followed u p during 1 year, it is possible that TI had been overlooked in some patients. To calculate the final improvement rate, TI was ranked into the category of no improvement. ComDlications. All traceable neurologic and general medical complications were registered as SRC if they had occurred within 2 months after a shunt. For subdural hematomas and hygromas, there was no time limit. Complications were classified as (1)seuere-death, ischemic or hemorrhagic strokes with marked deficit immediately after t h e event, intracranial infections, severe extracranial infections, subdural hematomas requiring surgery, poorly controlled epileptic seizures, and other rare complications; (2) moderate-ischemic or
hemorrhagic strokes with subsequent moderate deficit, symptomatic subdural hematomas not necessitating surgery, systemic infections without life-threatening signs, repeated epileptic fits, and other complications of moderate severity; or ( 3 ) mild-transient ischemic a t t a c k s , incidentally detected small asymptomatic infarcts or hemorrhages a t the site of the shunt implantation, incidentally detected asymptomatic subdural effusions, temporary CSF hypotension syndrome, one or sporadic epileptic fits, and other mild complications. Lack of improvement due to shunt dysfunction or a possible inappropriate s h u n t was separately listed because this was considered a failure of therapy rather than a complication. Residual morbidity following SRC was separately expressed on a transition scale: -2 = much worse; -1 = worse; 0 = no change. Death was considered as a SRC when it occurred within 2 months of the intervention and a n association with surgery was evident. The benefitharm ratio. The ratio of marked improvementlserious morbidity was calculated. This ratio was considered to be more appropriate in determining the final clinical outcome than the improvementkomplication ratio. Management strategies. Two neurosurgical centers were reputed for their strictness in considering patients with presumed NPH for a shunt. Although a flowchart to manage NPH was not used, only patients in whom NPH seemed probable on the basis of clinical and CT features, a positive response on CSF taps, and ventricular stasis on cisternography were shunted. This contrasted with the two other centers, in which shunting was regularly carried out either without performing ancillary tests or with liberal interpretation of these tests. In addition, a shunt was sometimes offered to patients with questionable NPH, based on the strategy of giving patients the “benefit of the doubt.” We calculated whether these two different strategies influenced the benefitharm ratio. Reuiew of the literature. The literature on adult NPH published between 1966 and 1990 was reviewed and the results of all suitable reports have been pooled to calculate the mean rate of improvement and complications following a shunt. To evaluate the impact of CTs and a decade of clinical and surgical experience, the results obtained between 1966 and 1976 and between 1977 and 1989 were calculated separately. Articles encompassing both decades were ranked into a separate category. ImDrovement. Inclusion criteria were that the articles h a d to describe postsurgical r e s u l t s i n at l e a s t 20 patients, and that the degree of improvement had to be ranked into a t least three categories, eg, none, some, or marked improvement. Smaller series were not included because sufficient details on improvement were given infrequently. Articles providing results overlapping both periods were listed apart. To assess the influence of etiology, improvement was separately calculated in series with only idiopathic NPH (INPH) and those containing both INPH and secondary NPH (SNPH), ie, NPH with a known etiology. ComDlications. To e s t i m a t e t h e r a t e of SRC, we included all reports describing 20 patients or more. The articles had to provide sufficient details on the type and severity of complications. SRC were classified as severe or mildmoderate; the available data did not permit separation of mild from moderate complications. When a complication could not be differentiated between moderate or severe, it was ranked as severe to avoid underestimation of SRC. When the same complication led to a cascade of January 1992 NEUROLOGY 42 55
adverse events, only the worst event was used to calculate the final SRC rate.
Results. Clinical study. Between January 1980 and July 1989, 17 neurosurgeons shunted 166 patients with presumed NPH, referred by 49 neurologists. The clinical profile of the patients varied from isolated gait impairment to the classical clinical triad of severe gait disturbances, dementia, and urinary incontinence. CTs showed ventricular enlargement ranging from mild to pronounced (frontal horn index 0.38 to 0.81). The decision to shunt a patient was based on clinical data, CTs, and frequently CSF-tap tests, cisternography, or both. Hydrodynamic studies including continuous intracranial pressure monitoring and lumbar or lumboventricular CSF infusion tests were performed only sporadically. Four patients were excluded because they had a n accompanying diagnosis which might have interfered with signs of NPH. Ten were excluded because their medical records were lost or did not contain sufficient information on postsurgical outcome. Hence, 152 patients remained for further analysis. The median age was 73 years (range, 33 to 86); 82 were men. The length of follow-up was 2 Table 1. Multicenter study: Improvement depending on etiology Etiology of NPH
No.
Idiopathic Known etiology, communicating Known etiology, noncommunicating
127 11
87
21
7
0
19 (15%) 4 (36%)
14
3
2
9 (64%)
Total
152
97 (64%)
23 115%)
Grades of improvement None Slight Marked
pts
32 (21%)
Percentages are rounded off upward or downward.
I
months to 8 years, median 3.1 years. ImDrovement. Table 1 provides information on improvement according to type of NPH. Cranial traumas were only included in the group with known etiology, when the relation with NPH was probable. Marked improvement occurred in 2 1% (95% confidence interval [CII 15-as%), lowering to 15% (95% CI 10-22%) when only patients with INPH were considered. This contrasted with the postsurgical outcome in SNPH (52%, 95% CI 3172%), increasing to 64% (95% CI 3547%) in the group of patients with noncommunicating NPH, of whom 13 of 14 had hydrocephalus due to aqueduct stenosis. Correlation of shunt types and opening pressures of the valves with grades of improvement showed that substantial improvement was obtained in 16% (95% CI 6-31%) with ventriculoperitoneal shunts (N = 38) and in 22% (95% CI 5 3 1 % ) with ventriculoatrial shunts (N = 113). Sixteen percent (95% CI 4-36%) of the patients with a high pressure valve (N = 25) and 22% (95% CI 14-35%) of those with a medium pressure valve (N = 110) markedly improved. In the remaining 17 patients, t h e opening pressure of t h e valve was low or unmentioned. As indicated by the 95% CI calculations, differences of outcome were significant neither for shunt types nor for the valve opening pressures. TI was noted in 43 patients. In 30 patients, TI did not last longer than 3 months, and in five it lasted more than 1year. TI represented 44% of the postsurgical success rate (43198). Complications. Table 2 lists the type and severity of complications and their impact on residual morbidity. Severe complications occurred in 24 patients, 22 with INPH and two with SNPH. The median age of the patients who died from SRC was 74 years (range, 70 to 86). The number of mild complications without residual deficit may be underestimated, as possibly not all mild complications were recorded.
Table 2. Multicenter study: Shunt-relatedcomplications and residual harm Total Ischemic strokes Cerebral hemorrhages Subdural hematomas and effusions Intracranial infections Epileptic seizures Extracranial infections Others Total
5 8 23
6 5 >25* >39*
Complications Severe Moderate
1
1
-
-
1 >18* >35*
4
-
-
>69* (45%)
9 (6%)
2 (1.3%)
2 2 11
4
2 2 3
-
4
4 2
>111*(73%) 24 (16%) 18 (12%)
* Exact data not available.
Residual harm Death Muchworse Worse
4
2 2 3
1
4 9
Percentages in parentheses are rounded up or down to the unit
56 NEUROLOGY 42 January 1992
Mild
No
2 2 2
2 1 21
1
1
4
-
-
1 2
5 >20*
>39*
10 (6.6%) >92*
Etiology of NPH
No. pts
Idiopathic Mixed(idiopathic + symptomatic)
272 775
47%) 32%
20% 18%
33% 50%
1,047
36%
18%
46%
Total
Grades of improvement None Slight Marked
. I
Shunt revisions. Forty-nine shunt revisions were performed in 32 patients. Eight revisions were carried out for symptomatic unilateral or bilateral subdural hematomas, four for proximal s h u n t infections, four for distal infections, and eight for shunt disconnection, displacement, or malposition. The remaining 25 revisions were carried out because lack of postsurgical improvement was attributed to shunt dysfunction. Multiple revisions took place in nine patients. Marked improvement following shunt revision was eventually obtained in five patients and some improvement in another five patients. Two revisions resulted in proximal shunt infections. Among the group of 10 patients with insufficient data, two shunts were revised. Residual morbiditv. Table 2 illustrates that the 28% severe and moderate complications eventually led to 13% residual morbidity of which about 7% were serious, ie, resulted in death or severe residual morbidity. All (N = 11) patients with serious residua belonged t o the group of INPH. Eight of them were in a poor presurgical condition. Insufficient data group. Ten patients (median age, 71 years; range, 66 to 79) were lost to followup. None of them improved during their stay at the neurosurgical department. Shunt revision was carried out in two patients and one patient had a severe complication. Substantial benefit/serious harm ratio (B/H ratio). The B/H ratio for the whole group was about three (32/11). Different management policies (strict selection versus liberal shunting) did not result in meaningful different B/H ratios: strict selection (N = 54) resulted in a B/H ratio of three (12/4, four deaths). A liberal shunting policy (N = 98) provided a B/H ratio of 2.85 (20/7, five deaths and two serious residual morbidity). In 23 patients in whom we could detect a combination of factors considered to highly increase the surgical risks, two patients substantially improved, one showed some improvement, six died, two markedly deteriorated, three displayed some residual morbidity, and nine remained unchanged, leading to a B/H ratio of only 0.25 (218). In the whole group of 152 patients, excluding these high-risk patients from surgery would have increased the B/H ratio to 10 (30 marked improvements/three serious morbidity). In the subgroup of INPH (N = 127), marked improvement occurred in 15%(19/127) and serious
harm in 8.6% (11/127), the B/H ratio was thus only 1.7. In this group, there were 106 patients who were good surgical risks; shunting only them would have led t o marked improvement in 17, slight improvement in 21, slight residual morbidity in six, three deaths, and a B/H ratio of about six (17/3). Literature. Improvement as reported in 19 articles accumulating 1,047 patients with INPH o r SNPH shunted between 1966 and 19894-22 is listed in table 3. It confirms the difference between outcome in idiopathic and “mixed NPH series, the latter containing about 50% of patients with SNPH. During the second decade, the overall improvement increased from 50 t o 74%) and marked improvement from 35 to 55%. The complications were calculated according to grade of severity and subdivided in two decades of shunting, published in 21 a r t i ~ l e s . ~In~ ~ ~ ~ all patients, ventriculoatrial o r ventriculoperitoneal shunts were used, except for two series in which all31or somezzpatients had lumboperitoneal shunts. During the first decade, the total number of complications was 35%) severe complications were 13%)and shunt dysfunction 14%. The second decade provided similar results: complications in 36%)of which 16% were severe, and shunt dysfunction in 13%. Thus, the rate of severe complications did not decrease during the second decade of shunting.
Discussion. Between 1966 and 1976, some publications on postsurgical results were disappointing, the rates of frank improvement frequently not exceeding 25 t o 30%.6-*Later, s h u n t i n g NPH seemed more rewarding, the mean rate of substantial improvement rising to 55%. It is tempting to attribute these better results t o increased diagnostic accuracy, the advent of CT, and improved surgical techniques. However, a series of biases may have been involved. To cite a few: most publications after 1976 came from the same expert neurologic or neurosurgical centers with special interest in NPH,13J5J6,zz whose results do not necessarily reflect those obtained in less experienced centers. Articles with positive results on the predictive value of (new) tests to select patients are more likely to be published than negative results. Some articles contain a biased preselected group of patients, eg, by considering for surgery only patients in whom shunt-responsive NPH was very probable on the basis of clinical and CT features.’*J* In other articles, the duration of follow-up was relatively short; this may inflate the results, as prolonged follow-up has shown a substantial drop in the number of improved p a t i e n t ~ . * J ~ . ~ ~ Selection and publication biases may thus have influenced the results obtained during the second decade of NPH surgery. To assess this assumption, we compared our results with those from the literature. Improuement. To calculate the real benefit of shunting, we included only patients who substanJanuary 1992 NEUROLOGY 42 57
tially improved, as in all but one patient with slight DO the benefits outweigh the harm? Review artiimprovement the benefit was of limited clinical cles on NPH o r t r e a t a b l e dementias r e m a i n importance. Marked improvement in our patient reserved in their advice to shunt potential NPH group was low (2l%), even lower when only INPH patients.34 Commenting on management problems was considered (15%).Comparing the results of the of reversible dementia, Clarfield46recently asserted two neurosurgical centers using strict selection crithat probably more harm than good is still done by teria with those obtained in two other centers with subjecting most NPH patients to a shunt procea liberal shunting policy showed no difference in dure. the improvement rate, suggesting that the two difPooled data of recent literature show that for ferent strategies had no influence on the improvethree o r four patients with substantial improvement rate. It is possible that using hydrodynamic ment one patient with a severe complication has to tests such as continuous intracranial CSF pressure be accepted. In our group with INPH, the price for m e a ~ u r e m e n t ~or~ a, ~lumboventricular ~,~~,~~ CSF one patient with substantial benefit was even infusion test13 would have led t o better results. much higher (BM ratio 1.7),but not shunting highHowever, these tests are of limited clinical value risk patients would have favorably increased the because of their invasiveness and complexity.38 B/H ratio. Less invasive tests such as cerebral blood flow Epidemiologic note. Our investigation illustrates mea~urements,’~ MR , ~ with ~ , ~ ~CSF flow s t ~ d i e s , ~ ~ , ~ ~shunt-responsive NPH remains a very rare that calculation of the ventricular/convexity CSF ratio,43 syndrome: in a referral population of about 2.5 miland continuous external lumbar CSF drainagez8 lion persons, we had only 55 NPH patients improvmust await validation. ing after a shunt in about 10 years. The incidence of shunt-responsive NPH in our particular area Temporary improvement. The high frequency of may be roughly e s t i m a t e d a t about temporary and short-lasting improvement, also observed by ~ t h e r is perplexing. ~ , ~ They ~ ~2.2/million/year, ~ ~ ~ and ~ only ~ about ~ ~1.3/million/year ~ ~ ~ for~ substantially improving NPH. represented nearly one-half of all immediate postsurgical improvements. There was no evidence of Conclusions. (1) The common opinion t h a t shunt dysfunction or underdrainage to explain this improvement of clinical importance in presumed INPH after a shunt will occur in 35 to 50% is optiphenomenon. S h u n t dysfunction may have mistic and may be influenced by a publication bias. remained undetected, however, if only assessed by I t is a reasonable assumption t h a t prolonged response to digital compression, which i s not improvement of clinical importance will be entirely reliable.44 obtained in only 15 t o 20%, mainly depending on Nonstandardized outcome criteria may have the etiology of NPH. (2) Many articles on NPH favored an overoptimistic immediate postsurgical mention percentages of complications, but few proevaluation, but it is probable that true, albeit tranvide extensive details on residual morbidity after 6 sient, improvement of undetermined origin did months, which is clinically more relevant. From occur. our data, we conclude that in patients with good Complications. Our clinical study confirms the risks, death and serious postsurgical morbidity will especially in assertion that the SRC rate is high,7,9,31 occur in about 2 to 3% of an unselected NPH popufrail patients.45The 27% complications in our group lation, but in 8 to 9% of patients with presumed led t o death or a serious morbidity in 7%. Many INPH. investigators have underscored the high number of complications, but only a few emphasized that most complications did not lead to permanent disabiliAcknowledgments ty.l43 This may lead to overestimation of the risks of shunting, as, from the patient’s point of view, We are most grateful to our colleagues from North Holland shunt-related events without residual harm have a whose kind collaboration was essential for this study. Professors limited clinical impact. Most patients who died or H. van Crevel and M. Vermeulen and Doctors G.A.G. Davies were left with serious postsurgical morbidity were and A. Hydra provided useful comments on previous drafts. in a poor presurgical condition. Shunting these patients was a desperate last-ditch effort. If shunting had not been performed in this group, serious References morbidity in the remaining patients would probably Hakim S, Adams RD. The special clinical problem of symphave been limited to 2 to 3%. In INPH, however, it tomatic hydrocephalus with normal cerebrospinal fluid presstill would have been 8 to 9%. sure: observations on cerebrospinal fluid hydrodynamics. J Shunt dysfunction and revisions. To include all Neurol Sci 1965;2:307-327. cases of shunt dysfunction in the list of SRC is conAdams RD, Fisher CM, Hakim S, Ojemann RG, Sweet WH. Symptomatic occult hydrocephalus with “normal” ceretroversial; lack of improvement due to shunt dysbrospinal fluid pressure: a treatable syndrome. N Engl J function or an inadequate shunt is rather a failure Med 1965;273:117-126. of therapy t h a n a complication. The benefit of Ojemann RG, Fisher CM, Adams RD, Sweet WH, New PFJ. shunt revisions in our group was limited, as five Further experience with the syndrome of “normal” pressure hydrocephalus. J Neurosurg 1969;31:279-294. shunt revisions were necessary to obtain one subSalmon JH. Adult hydrocephalus: evaluation of shunt therastantial benefit. 58 NEUROLOGY 42 January 1992
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25. Udvarhelyi GB, Wood JH, James AE Jr, et al. Results and complications in 55 shunted patients with normal pressure hydrocephalus. Surg Neurol 1975;3:271-275. 26. Magnaes B. Communicating hydrocephalus i n adults. Neurology 1978;28:478-484. 27. Hughes CP, Siege1 BA, Coxe WS, et al. Adult idiopathic communicating hydrocephalus with and without shunting. J Neurol Neurosurg Psychiatry 1978;41:961-971. 28. Haan J , Thomeer RTWM. Predictive value of temporary e x t e r n a l l u m b a r d r a i n a g e i n normal p r e s s u r e hydrocephalus. Neurosurgery 1988;22:388-391. 29. Spanu G, Sangiovanni G, Locatelli D. Normal-pressure hydrocephalus: twelve years experience. Neurochirurgia 1986;29:15-19. 30. Brasey DL, Fankhauser H, de Tribolet N. Hydrocephalie a pression normale chez I’adulte. Schweiz Med Wochenschr 1988;118:919-923. 31. Philippon J , Duplessis E, Dorwling-Carter D, Horn Y, Cornu Ph. Derivation lombo-pkritoneale et hydrocephalie a pression n o r m a l e d e s s u j e t s bges. Rev Neurol ( P a r i s ) 1989;11:776-780. 32. N o r m a l - p r e s s u r e h y d r o c e p h a l u s [editorial]. L a n c e t 1990;335:22-23. 33. Benzel EC, Pelletier AL, Levy PG. Communicating hydrocephalus in adults: prediction of outcome after ventricular shunting procedures. Neurosurgery 1990;26:655-660. 34. Pickard JD. Normal pressure hydrocephalus: to shunt or not to shunt. In: Warlow C, Garfield J , eds. Dilemmas in the m a n a g e m e n t of t h e neurological p a t i e n t . E d i n b u r g h : Churchill Livingstone, 1984:207-214. 35. Katzman R. Normal pressure hydrocephalus. In: Wells CE, ed. Dementia. 2nd ed. Philadelphia: FA Davis, 1977:69-92. 36. Symon L, Dorsch NWC, Stephans RJ. Pressure waves in socalled low-pressure hydrocephalus. Lancet 1972;2:12911292. 3 7 , C r o c k a r d HA, H a n l o n K, D u d a E E , M u l l a n J F . Hydrocephalus as a cause of dementia: evaluation of computerized tomography and intracranial pressure monitoring. J Neurol Neurosurg Psychiatry 1977;40:736-740. 38. Vanneste J , van Acker R. Normal pressure hydrocephalus: did literature influence management? J Neurol Neurosurg Psychiatry 1990;53:564-568. 39. Graff-Radford NR, Godersky JC, Jones MP. Variables predicting surgical outcome in symptomatic hydrocephalus in the elderly. Neurology 1989;39:1601-1604. 40. Hirai 0, Nishikawa M, Munaka M, e t al. 2311-IMP-SPECT and lumbar subarachnoid pressure in adult hydrocephalus. In: Hoff JT, Betz AL, eds. Intracranial pressure VII. Berlin: Springer- Verlag, 1989:425-430. 41. Bradley WG Jr, Kortman KE, Burgoyne B. Flowing cerebrospinal fluid in normal and hydrocephalic states: appearance on MR images. Radiology 1986;159:611-616. 42. Gamma1 TE, Allen MB, Brooks BS, Mark EK. MR evaluation of hydrocephalus. AJNR 1987;8:591-597. 43. Grant R, Condon B, Hadley DM, Teasdale GM. Intracranial CSF volume distribution in normal pressure hydrocephalus. In: Hoff JT, Betz AL, eds. Intracranial pressure VII. Berlin: Springer-Verlag, 1989:341-343. 44. Mirfakhrae M, Benzel EC, Crofford MJ, e t al. Metrizamide shuntography for evaluation of shunt malfunction in hydrocephalus. AJNR 1985;6:815-822. 45. Black P. Normal pressure hydrocephalus. In: Scott RM, ed. Hydrocephalus. Baltimore: Williams & Wilkins, 1990:109-114. 46. Clarfield AM. Normal-pressure hydrocephalus: saga or swamp? [editorial]. JAMA 1989;262:2592-2593.
January 1992 NEUROLOGY 42 59
Shunting normal−pressure hydrocephalus: Do the benefits outweigh the risks?: A multicenter study and literature review J. Vanneste, P. Augustijn, C. Dirven, et al. Neurology 1992;42;54 DOI 10.1212/WNL.42.1.54 This information is current as of January 1, 1992 Updated Information & Services
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Neurology ® is the official journal of the American Academy of Neurology. Published continuously since 1951, it is now a weekly with 48 issues per year. Copyright © 1992 by Edgell Communications, Inc.. All rights reserved. Print ISSN: 0028-3878. Online ISSN: 1526-632X.
Article abstract-We performed a multicenter retrospective study in 166 consecutive patients shunted for presumed normal-pressure hydrocephalus (NPH) in the four neurosurgical departments of Amsterdam. Overall improvement occurred in 36%, substantial improvement in 21%. In the subgroup of idiopathic NPH (N = 127), marked improvement was only 15%. The incidence of shunt-responsive NPH in our area was 2.2/million/year. The rate of severe and moderate shunt-related complications was 28%, leading to death or severe residual morbidity in 7%. The substantial benefit/serious harm ratio in the whole group was only three (21%/7%), decreasing to 1.7 in idiopathic NPH. By excluding patients at high surgical risk, this ratio might have risen to 10 in the whole group and to six in idiopathic NPH. Our experience is much less favorable than that encountered in the literature, reporting overall improvement in 74% and marked improvement in 55% of the shunted patients. We conclude that NPH is probably a very rare and still overdiagnosed syndrome and that the overall morbidity rate for each patient demonstrating meaningful improvement is high. NEUROLOGY 1992;42:54-59
between the benefits and the surgical risks, we carGait disturbances, mental impairment, and uriried out this study to answer three questions: nary urgency o r incontinence associated with 1. A clinical study: What are the benefit and hydrocephalus and normal pressure at lumbar puncture may be reversed by CSF d i ~ e r s i 0 n . l . ~ complication rates calculated from the results of a retrospective multicenter study on all patients Twenty-five years after the first description of the shunted for presumed NPH? syndrome of normal-pressure hydrocephalus 2. A literature study: What is the expected rate (NPH), the therapeutic approach remains problemof improvement and complications in shunted NPH atic. Clinicians still waver between the fear of patients when the data from the appropriate literamissing a treatable dementia or gait disorder and ture published between 1966 and 1990 are pooled? the reluctance to submit their presumed NPH 3. A comparison of studies 1 and 2 (above): What patients to the risks of ventricular drainage. are the similarities and discrepancies and the conManagement is based mainly on articles providsequences for clinical practice? ing data on percentages of benefit*-22and shuntThe varirelated complications (SRC).4,6-9,12-16,19,23-31 Methods. Clinical study. Patients. All neurosurgical and ability of clinical response is considerable: mean neurologic charts, available CTs, and cisternograms of rates of improvement average 50%,9,22,31 with wide 166 consecutive patients with a n admission diagnosis of SRC occur in 30 t o variations from 25 to 80%.6J8,32,33 NPH, shunted between January 1980 and July 1989 in 40% of patients, but comments on complications the four neurosurgical departments of Amsterdam, were vary from reassuring remarks on the reversibility reviewed. The departments consist of two university of most complications8J4J6t o alarming comments departments of neurosurgery and two neurosurgical seron the frequency of shunt-related disaster^.^^^^^ The vices in teaching hospitals-together the referral neurovariability of clinical details on complications, more surgical centers for a population of about 2.5 million peoparticularly their impact on residual morbidity, ple. To clarify uncertainties on clinical outcome, we also reviewed the notes of the nursing staff and contacted by may have contributed to these divergent estimatelephone some patients, their family, or the general tiorm31 practitioner. We considered the diagnosis of NPH if the As controversy persists regarding t h e ratio
From the Department of Neurology (J. Vanneste, P. Augustijn), St. Lucasziekenhuis; the Department of Neurosurgery (C. Dirvenj, Academic Hospital, Free University of Amsterdam; the Department of Neurosurgery (W.F. Tan), Academic Medical Centre, University of Amsterdam; and the Department of Neurosurgery (Z.D. Goedhart), Municipal Hospital Slotervaart, Amsterdam, The Netherlands. Received March 6, 1991. Accepted for publication in final form June 17, 1991 Address correspondence and reprint requests to Dr. J. Vanneste, Department of Neurology, St. Lucasziekenhuis 164, 1061 AE Amsterdam, The Netherlands. 54 NEUROLOGY 42 January 1992
clinical and CT criteria were met as has been previously des~ribed.~,~.~~.~~ Clinical characteristics. As far as possible, gait disturbances were graded on an ordinal scale with five categories: normal (0); unstable, but still independent gait (la), or small-stepped, independent gait ( l b ) ; walking with some aid (eg, cane) ( 2 ) ; walking with substantial aid (eg, two canes or a walker) ( 3 ) ; and walking not possible, wheelchair-bound (4).Mental impairment was divided into four categories: no apparent dementia (O), mild mental slowness and memory disturbances ( l ) , moderately severe mental impairment (21, and severe dementia (3). When cognitive impairment included cortical dysfunction such as aphasia, apraxia and agnosia, it was separately recorded. Bladder disturbances were ranked into three categories: absent (0), increased urinary frequency (l), and incontinence (2). When expression in one category was not possible on the basis of available data, two contiguous categories were used, eg, gait 213. The general condition and the presence of diseases considered to increase the surgical risks were noted. As this is a retrospective study, we could not find sufficient details to quantify t h e risks of anesthesia or neurosurgery. Despite this, we estimated that patients were at high surgical risks when they had a combination of three of the following variables: cardiac dysrhythmia, a history of recent myocardial infarction, pulmonary obstructive disease requiring medication, a history of one or more major strokes, and other rare conditions such as a histor y of recurrent lung embolisms requiring anticoagulant therapy. Improvement. Improvement was rated as follows: no effect (0); some improvement ( + l ) , when gait disturbance, mental impairment, or both ameliorated 1 point on the ordinal scale, or when the patient, his or her family, and t h e neurologist agreed t h a t there was slight improvement, but less than 1grade on the ordinal scales, eg, a n unstable, independent gait (grade 1)becoming less unstable after shunting. Marked improvement (+2) implied that gait, mental disturbances, or both ameliorated 2 points or more on the ordinal scale, or when the patient, the nurses, and the neurologist estimated that shunting had been followed by a substantial clinical improvement. All improvements had to be confirmed by two independent assessors. Duration of improvement was also registered; it was considered as definitive either in patients whose improvement persisted until the last follow-up (but at least for 1year), or in patients who died earlier or were incapacitated by unrelated causes but had remained improved for at least 6 months. When improvement was followed by relapse t h a t did not respond to shunt revisions or other therapeutic meas u r e s , it was categorized s e p a r a t e l y as t e m p o r a r y improvement (TI), even when NPH recurred after 1year or longer. As not all patients were followed u p during 1 year, it is possible that TI had been overlooked in some patients. To calculate the final improvement rate, TI was ranked into the category of no improvement. ComDlications. All traceable neurologic and general medical complications were registered as SRC if they had occurred within 2 months after a shunt. For subdural hematomas and hygromas, there was no time limit. Complications were classified as (1)seuere-death, ischemic or hemorrhagic strokes with marked deficit immediately after t h e event, intracranial infections, severe extracranial infections, subdural hematomas requiring surgery, poorly controlled epileptic seizures, and other rare complications; (2) moderate-ischemic or
hemorrhagic strokes with subsequent moderate deficit, symptomatic subdural hematomas not necessitating surgery, systemic infections without life-threatening signs, repeated epileptic fits, and other complications of moderate severity; or ( 3 ) mild-transient ischemic a t t a c k s , incidentally detected small asymptomatic infarcts or hemorrhages a t the site of the shunt implantation, incidentally detected asymptomatic subdural effusions, temporary CSF hypotension syndrome, one or sporadic epileptic fits, and other mild complications. Lack of improvement due to shunt dysfunction or a possible inappropriate s h u n t was separately listed because this was considered a failure of therapy rather than a complication. Residual morbidity following SRC was separately expressed on a transition scale: -2 = much worse; -1 = worse; 0 = no change. Death was considered as a SRC when it occurred within 2 months of the intervention and a n association with surgery was evident. The benefitharm ratio. The ratio of marked improvementlserious morbidity was calculated. This ratio was considered to be more appropriate in determining the final clinical outcome than the improvementkomplication ratio. Management strategies. Two neurosurgical centers were reputed for their strictness in considering patients with presumed NPH for a shunt. Although a flowchart to manage NPH was not used, only patients in whom NPH seemed probable on the basis of clinical and CT features, a positive response on CSF taps, and ventricular stasis on cisternography were shunted. This contrasted with the two other centers, in which shunting was regularly carried out either without performing ancillary tests or with liberal interpretation of these tests. In addition, a shunt was sometimes offered to patients with questionable NPH, based on the strategy of giving patients the “benefit of the doubt.” We calculated whether these two different strategies influenced the benefitharm ratio. Reuiew of the literature. The literature on adult NPH published between 1966 and 1990 was reviewed and the results of all suitable reports have been pooled to calculate the mean rate of improvement and complications following a shunt. To evaluate the impact of CTs and a decade of clinical and surgical experience, the results obtained between 1966 and 1976 and between 1977 and 1989 were calculated separately. Articles encompassing both decades were ranked into a separate category. ImDrovement. Inclusion criteria were that the articles h a d to describe postsurgical r e s u l t s i n at l e a s t 20 patients, and that the degree of improvement had to be ranked into a t least three categories, eg, none, some, or marked improvement. Smaller series were not included because sufficient details on improvement were given infrequently. Articles providing results overlapping both periods were listed apart. To assess the influence of etiology, improvement was separately calculated in series with only idiopathic NPH (INPH) and those containing both INPH and secondary NPH (SNPH), ie, NPH with a known etiology. ComDlications. To e s t i m a t e t h e r a t e of SRC, we included all reports describing 20 patients or more. The articles had to provide sufficient details on the type and severity of complications. SRC were classified as severe or mildmoderate; the available data did not permit separation of mild from moderate complications. When a complication could not be differentiated between moderate or severe, it was ranked as severe to avoid underestimation of SRC. When the same complication led to a cascade of January 1992 NEUROLOGY 42 55
adverse events, only the worst event was used to calculate the final SRC rate.
Results. Clinical study. Between January 1980 and July 1989, 17 neurosurgeons shunted 166 patients with presumed NPH, referred by 49 neurologists. The clinical profile of the patients varied from isolated gait impairment to the classical clinical triad of severe gait disturbances, dementia, and urinary incontinence. CTs showed ventricular enlargement ranging from mild to pronounced (frontal horn index 0.38 to 0.81). The decision to shunt a patient was based on clinical data, CTs, and frequently CSF-tap tests, cisternography, or both. Hydrodynamic studies including continuous intracranial pressure monitoring and lumbar or lumboventricular CSF infusion tests were performed only sporadically. Four patients were excluded because they had a n accompanying diagnosis which might have interfered with signs of NPH. Ten were excluded because their medical records were lost or did not contain sufficient information on postsurgical outcome. Hence, 152 patients remained for further analysis. The median age was 73 years (range, 33 to 86); 82 were men. The length of follow-up was 2 Table 1. Multicenter study: Improvement depending on etiology Etiology of NPH
No.
Idiopathic Known etiology, communicating Known etiology, noncommunicating
127 11
87
21
7
0
19 (15%) 4 (36%)
14
3
2
9 (64%)
Total
152
97 (64%)
23 115%)
Grades of improvement None Slight Marked
pts
32 (21%)
Percentages are rounded off upward or downward.
I
months to 8 years, median 3.1 years. ImDrovement. Table 1 provides information on improvement according to type of NPH. Cranial traumas were only included in the group with known etiology, when the relation with NPH was probable. Marked improvement occurred in 2 1% (95% confidence interval [CII 15-as%), lowering to 15% (95% CI 10-22%) when only patients with INPH were considered. This contrasted with the postsurgical outcome in SNPH (52%, 95% CI 3172%), increasing to 64% (95% CI 3547%) in the group of patients with noncommunicating NPH, of whom 13 of 14 had hydrocephalus due to aqueduct stenosis. Correlation of shunt types and opening pressures of the valves with grades of improvement showed that substantial improvement was obtained in 16% (95% CI 6-31%) with ventriculoperitoneal shunts (N = 38) and in 22% (95% CI 5 3 1 % ) with ventriculoatrial shunts (N = 113). Sixteen percent (95% CI 4-36%) of the patients with a high pressure valve (N = 25) and 22% (95% CI 14-35%) of those with a medium pressure valve (N = 110) markedly improved. In the remaining 17 patients, t h e opening pressure of t h e valve was low or unmentioned. As indicated by the 95% CI calculations, differences of outcome were significant neither for shunt types nor for the valve opening pressures. TI was noted in 43 patients. In 30 patients, TI did not last longer than 3 months, and in five it lasted more than 1year. TI represented 44% of the postsurgical success rate (43198). Complications. Table 2 lists the type and severity of complications and their impact on residual morbidity. Severe complications occurred in 24 patients, 22 with INPH and two with SNPH. The median age of the patients who died from SRC was 74 years (range, 70 to 86). The number of mild complications without residual deficit may be underestimated, as possibly not all mild complications were recorded.
Table 2. Multicenter study: Shunt-relatedcomplications and residual harm Total Ischemic strokes Cerebral hemorrhages Subdural hematomas and effusions Intracranial infections Epileptic seizures Extracranial infections Others Total
5 8 23
6 5 >25* >39*
Complications Severe Moderate
1
1
-
-
1 >18* >35*
4
-
-
>69* (45%)
9 (6%)
2 (1.3%)
2 2 11
4
2 2 3
-
4
4 2
>111*(73%) 24 (16%) 18 (12%)
* Exact data not available.
Residual harm Death Muchworse Worse
4
2 2 3
1
4 9
Percentages in parentheses are rounded up or down to the unit
56 NEUROLOGY 42 January 1992
Mild
No
2 2 2
2 1 21
1
1
4
-
-
1 2
5 >20*
>39*
10 (6.6%) >92*
Etiology of NPH
No. pts
Idiopathic Mixed(idiopathic + symptomatic)
272 775
47%) 32%
20% 18%
33% 50%
1,047
36%
18%
46%
Total
Grades of improvement None Slight Marked
. I
Shunt revisions. Forty-nine shunt revisions were performed in 32 patients. Eight revisions were carried out for symptomatic unilateral or bilateral subdural hematomas, four for proximal s h u n t infections, four for distal infections, and eight for shunt disconnection, displacement, or malposition. The remaining 25 revisions were carried out because lack of postsurgical improvement was attributed to shunt dysfunction. Multiple revisions took place in nine patients. Marked improvement following shunt revision was eventually obtained in five patients and some improvement in another five patients. Two revisions resulted in proximal shunt infections. Among the group of 10 patients with insufficient data, two shunts were revised. Residual morbiditv. Table 2 illustrates that the 28% severe and moderate complications eventually led to 13% residual morbidity of which about 7% were serious, ie, resulted in death or severe residual morbidity. All (N = 11) patients with serious residua belonged t o the group of INPH. Eight of them were in a poor presurgical condition. Insufficient data group. Ten patients (median age, 71 years; range, 66 to 79) were lost to followup. None of them improved during their stay at the neurosurgical department. Shunt revision was carried out in two patients and one patient had a severe complication. Substantial benefit/serious harm ratio (B/H ratio). The B/H ratio for the whole group was about three (32/11). Different management policies (strict selection versus liberal shunting) did not result in meaningful different B/H ratios: strict selection (N = 54) resulted in a B/H ratio of three (12/4, four deaths). A liberal shunting policy (N = 98) provided a B/H ratio of 2.85 (20/7, five deaths and two serious residual morbidity). In 23 patients in whom we could detect a combination of factors considered to highly increase the surgical risks, two patients substantially improved, one showed some improvement, six died, two markedly deteriorated, three displayed some residual morbidity, and nine remained unchanged, leading to a B/H ratio of only 0.25 (218). In the whole group of 152 patients, excluding these high-risk patients from surgery would have increased the B/H ratio to 10 (30 marked improvements/three serious morbidity). In the subgroup of INPH (N = 127), marked improvement occurred in 15%(19/127) and serious
harm in 8.6% (11/127), the B/H ratio was thus only 1.7. In this group, there were 106 patients who were good surgical risks; shunting only them would have led t o marked improvement in 17, slight improvement in 21, slight residual morbidity in six, three deaths, and a B/H ratio of about six (17/3). Literature. Improvement as reported in 19 articles accumulating 1,047 patients with INPH o r SNPH shunted between 1966 and 19894-22 is listed in table 3. It confirms the difference between outcome in idiopathic and “mixed NPH series, the latter containing about 50% of patients with SNPH. During the second decade, the overall improvement increased from 50 t o 74%) and marked improvement from 35 to 55%. The complications were calculated according to grade of severity and subdivided in two decades of shunting, published in 21 a r t i ~ l e s . ~In~ ~ ~ ~ all patients, ventriculoatrial o r ventriculoperitoneal shunts were used, except for two series in which all31or somezzpatients had lumboperitoneal shunts. During the first decade, the total number of complications was 35%) severe complications were 13%)and shunt dysfunction 14%. The second decade provided similar results: complications in 36%)of which 16% were severe, and shunt dysfunction in 13%. Thus, the rate of severe complications did not decrease during the second decade of shunting.
Discussion. Between 1966 and 1976, some publications on postsurgical results were disappointing, the rates of frank improvement frequently not exceeding 25 t o 30%.6-*Later, s h u n t i n g NPH seemed more rewarding, the mean rate of substantial improvement rising to 55%. It is tempting to attribute these better results t o increased diagnostic accuracy, the advent of CT, and improved surgical techniques. However, a series of biases may have been involved. To cite a few: most publications after 1976 came from the same expert neurologic or neurosurgical centers with special interest in NPH,13J5J6,zz whose results do not necessarily reflect those obtained in less experienced centers. Articles with positive results on the predictive value of (new) tests to select patients are more likely to be published than negative results. Some articles contain a biased preselected group of patients, eg, by considering for surgery only patients in whom shunt-responsive NPH was very probable on the basis of clinical and CT features.’*J* In other articles, the duration of follow-up was relatively short; this may inflate the results, as prolonged follow-up has shown a substantial drop in the number of improved p a t i e n t ~ . * J ~ . ~ ~ Selection and publication biases may thus have influenced the results obtained during the second decade of NPH surgery. To assess this assumption, we compared our results with those from the literature. Improuement. To calculate the real benefit of shunting, we included only patients who substanJanuary 1992 NEUROLOGY 42 57
tially improved, as in all but one patient with slight DO the benefits outweigh the harm? Review artiimprovement the benefit was of limited clinical cles on NPH o r t r e a t a b l e dementias r e m a i n importance. Marked improvement in our patient reserved in their advice to shunt potential NPH group was low (2l%), even lower when only INPH patients.34 Commenting on management problems was considered (15%).Comparing the results of the of reversible dementia, Clarfield46recently asserted two neurosurgical centers using strict selection crithat probably more harm than good is still done by teria with those obtained in two other centers with subjecting most NPH patients to a shunt procea liberal shunting policy showed no difference in dure. the improvement rate, suggesting that the two difPooled data of recent literature show that for ferent strategies had no influence on the improvethree o r four patients with substantial improvement rate. It is possible that using hydrodynamic ment one patient with a severe complication has to tests such as continuous intracranial CSF pressure be accepted. In our group with INPH, the price for m e a ~ u r e m e n t ~or~ a, ~lumboventricular ~,~~,~~ CSF one patient with substantial benefit was even infusion test13 would have led t o better results. much higher (BM ratio 1.7),but not shunting highHowever, these tests are of limited clinical value risk patients would have favorably increased the because of their invasiveness and complexity.38 B/H ratio. Less invasive tests such as cerebral blood flow Epidemiologic note. Our investigation illustrates mea~urements,’~ MR , ~ with ~ , ~ ~CSF flow s t ~ d i e s , ~ ~ , ~ ~shunt-responsive NPH remains a very rare that calculation of the ventricular/convexity CSF ratio,43 syndrome: in a referral population of about 2.5 miland continuous external lumbar CSF drainagez8 lion persons, we had only 55 NPH patients improvmust await validation. ing after a shunt in about 10 years. The incidence of shunt-responsive NPH in our particular area Temporary improvement. The high frequency of may be roughly e s t i m a t e d a t about temporary and short-lasting improvement, also observed by ~ t h e r is perplexing. ~ , ~ They ~ ~2.2/million/year, ~ ~ ~ and ~ only ~ about ~ ~1.3/million/year ~ ~ ~ for~ substantially improving NPH. represented nearly one-half of all immediate postsurgical improvements. There was no evidence of Conclusions. (1) The common opinion t h a t shunt dysfunction or underdrainage to explain this improvement of clinical importance in presumed INPH after a shunt will occur in 35 to 50% is optiphenomenon. S h u n t dysfunction may have mistic and may be influenced by a publication bias. remained undetected, however, if only assessed by I t is a reasonable assumption t h a t prolonged response to digital compression, which i s not improvement of clinical importance will be entirely reliable.44 obtained in only 15 t o 20%, mainly depending on Nonstandardized outcome criteria may have the etiology of NPH. (2) Many articles on NPH favored an overoptimistic immediate postsurgical mention percentages of complications, but few proevaluation, but it is probable that true, albeit tranvide extensive details on residual morbidity after 6 sient, improvement of undetermined origin did months, which is clinically more relevant. From occur. our data, we conclude that in patients with good Complications. Our clinical study confirms the risks, death and serious postsurgical morbidity will especially in assertion that the SRC rate is high,7,9,31 occur in about 2 to 3% of an unselected NPH popufrail patients.45The 27% complications in our group lation, but in 8 to 9% of patients with presumed led t o death or a serious morbidity in 7%. Many INPH. investigators have underscored the high number of complications, but only a few emphasized that most complications did not lead to permanent disabiliAcknowledgments ty.l43 This may lead to overestimation of the risks of shunting, as, from the patient’s point of view, We are most grateful to our colleagues from North Holland shunt-related events without residual harm have a whose kind collaboration was essential for this study. Professors limited clinical impact. Most patients who died or H. van Crevel and M. Vermeulen and Doctors G.A.G. Davies were left with serious postsurgical morbidity were and A. Hydra provided useful comments on previous drafts. in a poor presurgical condition. Shunting these patients was a desperate last-ditch effort. If shunting had not been performed in this group, serious References morbidity in the remaining patients would probably Hakim S, Adams RD. The special clinical problem of symphave been limited to 2 to 3%. In INPH, however, it tomatic hydrocephalus with normal cerebrospinal fluid presstill would have been 8 to 9%. sure: observations on cerebrospinal fluid hydrodynamics. J Shunt dysfunction and revisions. To include all Neurol Sci 1965;2:307-327. cases of shunt dysfunction in the list of SRC is conAdams RD, Fisher CM, Hakim S, Ojemann RG, Sweet WH. Symptomatic occult hydrocephalus with “normal” ceretroversial; lack of improvement due to shunt dysbrospinal fluid pressure: a treatable syndrome. N Engl J function or an inadequate shunt is rather a failure Med 1965;273:117-126. of therapy t h a n a complication. 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Shunting normal−pressure hydrocephalus: Do the benefits outweigh the risks?: A multicenter study and literature review J. Vanneste, P. Augustijn, C. Dirven, et al. Neurology 1992;42;54 DOI 10.1212/WNL.42.1.54 This information is current as of January 1, 1992 Updated Information & Services
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