Normal-Pressure Is

Cisternography Still

Useful in

Hydrocephalus Selecting Patients for a Shunt?

Jan Vanneste, MD; Paul Augustijn, MD; Gareth A. G. Davies, FRCR; Clemens Dirven, MD; Wee Fu Tan, MD The clinical usefulness of cisternography in selecting pa¬ tients with presumed normal-pressure hydrocephalus for shunting was investigated in 76 patients. The predictive value of a scale based on combined clinical and computed tomographic criteria was first established, followed by an assessment of the predictive value of cisternography. Pre¬ dictions based on cisternograms were identical to those of the clinical/computed tomographic scale in 43%, better in 24%, and worse in 33%. Our findings suggest that cister¬ nography does not improve the diagnostic accuracy of combined clinical and computed tomographic criteria in patients with presumed normal-pressure hydrocephalus. (Arch Neurol. 1992;49:366-370) •

hydrocephalus (NPH) combines clinical triad consisting of gait disturbances, mental Normal-pressure chronic deterioration, and a

urinary incontinence with hy¬ due to drocephalus impaired circulation of the cerebrospi¬ nal fluid (CSF) and normal pressure on lumbar puncture.13 One of the techniques used to detect disturbed CSF circu¬ lation in NPH is cisternography, with intrathecal injection of either a radioactive isotope (isotope cisternography)4"6 or nonionic contrast material and serial computed tomo¬

graphic (CT) scanning (CT cisternography).7,8 The usefulness of cisternography in selecting patients with presumed NPH for shunting remains controversial. Some publications on NPH described the test as useful in providing additional information,9"13 but many others found that the predictive accuracy of cisternography was low or even did not use the test.14"24 Despite this, cister¬ nography remains one of the most popular tests in detecting NPH.25 One of the reasons may be that most clinicians have no access to more predictive but techni¬ cally complex tests, and that performing cisternography is better than making a therapeutic decision on the basis of clinical and CT criteria alone. In this study, we aimed Accepted

for publication August 21, 1991. From the Departments of Neurology (Drs Vanneste and Augustijn) and Neuroradiology (Dr Davies), St Lucasziekenhuis, Amster¬ dam, the Netherlands; Department of Neurosurgery, Academic Hospital, Free University of Amsterdam (Dr Dirven); and Depart¬ ment of Neurosurgery, Academic Medical Centre, University of Amsterdam (Dr Tan). Reprint requests to Department of Neurology, St Lucaszieken¬ huis, J Tooropstr 164, 1061 AE Amsterdam, the Netherlands (Dr

Vanneste).

at

investigating this assumption by calculating the addi¬

tional

predictive value of cisternography, as many inves¬

tigators calculated its predictive value but, to the best of our knowledge, did not investigate whether cisternogra¬

phy would increase the diagnostic accuracy of combined clinical and CT criteria.

PATIENTS AND METHODS Patients The medical charts of all patients who underwent shunting between 1980 and 1989 for presumed NPH in the four neurosur¬ gical departments of Amsterdam (the Netherlands) were re¬ viewed. Assessment of the clinical data included the cause of NPH, time of onset, rate of progression and severity of gait dis¬ order, mental impairment, and bladder dysfunction; predomi¬ nance of one of the three "classic" signs; the presence of signs not consistent with NPH; evidence of cerebrovascular disease; presence of other diseases explaining (at least partially) the clin¬ ical picture; and coexisting diseases affecting the general condi¬ tion. Data on the clinical outcome after shunting surgery were collected from the medical records, and, in cases of doubt, the notes of the nursing staff were also reviewed and the patients, their family, or the general practitioner were telephoned to pro¬ vide additional information.

CT Scans The following measurements were made: frontal horn index (the ratio between the maximal width of the frontal horns and the width of the whole brain at the same level); roundness of the frontal horns (0, not rounded; 1, slightly rounded; and 2, mark¬ edly rounded); lateral ventricle index (the ratio between the width of the lateral ventricle at the level of the pars centralis and the width of the whole brain at the same level); third ventricle index (the maximal width of the third ventricle divided by the width of the brain at the same level); and width of the temporal horns, expressed as follows: grade 0, not seen; grade 1, slightly enlarged; and grade 2, markedly enlarged. Convexity sulci were

graded as not present (0), present (1), enlarged (2), or markedly enlarged (3); the fourth ventricle was rated as normal or enlarged. Periventricular frontal or occipital lucencies were

noted as present or absent. The presence of white-matter lucen¬ cies (WMLs) was rated as follows: no lucencies, 0; discrete and sporadic WMLs, 1; moderate WMLs, 2; and pronounced and diffusely distributed WMLs, 3. Stages 2 and 3 were considered consistent with subcortical arteriosclerotic encephalopathy. La¬ cunar lesions in the white matter were separately recorded. Dif¬ ferentiation of periventricular transependymal CSF effusion from subcortical arteriosclerotic encephalopathy was based on

defined criteria.26·27

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Cisternography All available cisternographies were reassessed with "blinding" to the original reports. In cases of controversy or doubt concern¬ ing the original reports, a third independent opinion was obtained. Isotope cisternograms were carried out with either iodinated 1131 serum albumin or indium In 111 pentetate. The CT cisternograms consisted of lumbar intrathecal injection of watersoluble nonionic contrast material (metrizamide, iopamidol, or iohexol). The results of the radioisotope and CT cisternograms were combined because these two methods provide similar in¬ formation on CSF flow.28"31 The concentration of the isotope or the contrast material in the ventricles, the sylvian fissure, and the parasagittal areas was es¬ timated visually 6, 24, and 48 hours after injection and classified as (1) slight, (2) moderate, or (3) marked. Cisternograms of poor technical quality or containing insufficient information (eg, last views only 24 hours after contrast injection) were excluded.

Predictive Value of the Clinical/CT Scale The preoperative clinical data and CT measurements were combined into an ordinal global clinical/CT scale with blinding to the results of ancillary tests and to the outcome after shunt¬ ing. This scale was established by combining a number of clin¬ ical and CT variables because a recent study on management of NPH had confirmed our presumption that most neurologists base their therapeutic decisions mainly on clinical and CT infor¬ mation combined in a global estimation.25 We thus established the categories of a clinical/CT scale by combining clinical and CT variables that, according to the appropriate literature and our own experience, seemed to be the most reliable predictors in selecting patients for a shunt. For ex¬ ample, it is now commonly accepted that gait impairment as the first or predominant sign increases the probability of NPH. As Feinstein32 suggested, we found that a global scale may be a "satisfactory compromise between consistency needed for gen¬ eral science, suitability needed for clinical communication and simplicity needed for pragmatic clinical usage." The clinical/CT scale contained three categories, expressing the degree of probability that a patient would improve after a shunt (shunt-responsive NPH [SR-NPH]); SR-NPH was consid¬ ered (1) probable, (2) possible, or (3) improbable. Criteria used to allocate patients to one of the three categories were as follows. Probable SR-NPH.— Clinical criteria included the combination of the following characteristics: gait disturbances that predom¬ inated or were the first sign; mental impairment ranging from not clinically present to moderate; and absence of another dis¬ ease that might explain the clinical symptoms. The presence of urinary incontinence, known cause, and rapid clinical progression further increased the probability of NPH but were not necessary to allocate a patient to this category. The CT criteria included the combination of rounded frontal horns plus at least moderate ventriculomegaly (frontal horn in¬ dex, 0.40 or higher) plus absence of severe cortical atrophy (Sulci, 0 or 1) plus absence of severe WMLs. Marked enlargement of the temporal horns and third ventricle further increased the proba¬ bility but was not a necessary feature. A frontal horn index of 0.40 or more was chosen because, before this study, we had had unfavorable experiences with shunting in patients with only slightly dilated ventricles. A frontal horn index of 0.40 was cho¬ sen as the arbitrary cutoff point between slightly and moderately enlarged ventricles. Possible SR-NPH. —This category included all patients who could not be classified as having probable or improbable SRNPH, eg, the CT displayed moderate or pronounced WMLs, but it was not sufficient to explain severe ventriculomegaly. Possi¬ ble combinations of two diseases, such as subcortical arterio¬ sclerotic encephalopathy and NPH or Alzheimer's disease and NPH, were ranked in this category. Improbable SR-NPH.— Clinical criteria included one of the fol¬ lowing characteristics: absence of gait disturbances; marked predominance of dementia; dementia characterized by predom-

dysfunction, such as aphasia or agnosia; and presence of another disease explaining the total clinical picture (eg, subcortical arteriosclerotic encephalopathy). The CT criteria included one of the following variables: only slightly dilated ventricles (frontal horn index, )

10§



43 (57)

10

11+

32

18

75 (100)

Probable

Possible

Improbable

13+

5

1

7+





3+

2

20

Probable

Possible

8 9 16 4 Total both "Possible" "Probable" from Table includes and The "Probable" category 1. +Same prediction (n 34). fBetter prediction with cisternography (n 18). § Worse prediction with cisternography (n 23).

(43)

=

=

=

Table 3.—Correlations of Clinical/Computed

Tomographic (CT) and Cisternography Scales in

Communicating Hydrocephalus Determination

Improved

Cisternographic Determination

Probable

(n

=

by Clinical/CT Scale,

No.

Unimproved (n 45)

19)

=

Possible

Improbable

I

Probable

Possible

Total,

Improbable

No. (%) 21 (33)

Probable

1*

3+

1+

5*

6

5

Possible

4

r

0+

1+

3*

2

11 (17)

Improbable

3

3

3*

2+

10+

11*

32 (50)

4

8

19

18

64 (100)

8 7 Total *Same prediction (n 24). +Better prediction with cisternography (n 17). tWorse prediction with cisternography (n 23). =

=

=

SR-NPH. Quite similar predictive values would have been obtained: no additional information in 34 patients (45%; 95% CI, 34% to 57%), better predictions in 18 (24%; 95% CI, 15% to 35%), and worse predictions in 23 (31%; 95% CI, 21% to 42%).

Additional Predictive Value in Communicating NPH Table 3 correlates predictions of the clinical/CT scale with those of cisternography in the subgroup of commu¬ nicating NPH. In this subgroup with higher diagnostic uncertainty and a lower rate of improvement, cisternog¬ raphy had no additional predictive value, the number of worse predictions (n 23) remaining higher than that of better predictions (n=17). =

COMMENT and experts in the fields of CSF hy¬ and treatable dementia have aban¬

Most investigators drodynamics, NPH, doned cisternography

as a

diagnostic procedure.18-21"23

This contrasts with common practice, as most clinicians still use cisternography to obtain additional diagnostic in¬ formation; in a recent survey on management of NPH, we found that 50% of the neurologists interviewed still used cisternography to decrease diagnostic uncertainty, and that many believed that the pattern of ventricular reflux for 24 or 48 hours increased the probability of SR-NPH.25 The main reasons that is still in vogue may be that complex and often invasive techniques with a higher predictive value are inaccessible to most centers, and that many clinicians believe that cisternography is still valuable to decrease the diagnostic uncertainty re¬ maining after clinical and CT assessment, especially when the effect of one or more CSF taps was inconclusive.

cisternography

In the present series, it was striking that only 14 of the 32 patients with cisternograms classified as showing prob¬ able SR-NPH improved. This contrasts with the of Black et al,38 who noted that a "positive" test may be

findings

helpful.

This high rate of false-positive results suggests that there is no "classic" cisternographic pattern of NPH. It was also remarkable that in five patients displaying clinical and CT characteristics highly suggestive of hy¬ drocephalus ex vacuo associated with cerebral degenera¬ tive disease, a cisternographic pattern suggestive of probable SR-NPH was found. This does not confirm the opinion that, in cerebral atrophy, ventricular reflux is fre¬ quent but does not persist for 48 hours. As has been previously demonstrated,38 the rate of false-negative results was also disappointingly high; avoiding shunting in all patients with improbable SRNPH would have led to withholding 28% of this subgroup from a successful surgical procedure. Another point of discussion is that cisternography may have been useful in the subgroup of patients with communicating NPH, as this is the group leaving the cli¬ nician with the highest diagnostic uncertainty after clin¬ ical and CT evaluation. Table 3 shows that, even in this group, cisternography would have led to more wrong than right therapeutic decisions. To reduce biases associated with retrospective studies, we carried out this study in a "retrolective" way32; although this is a retrospective cohort study, we prospec¬ tively evaluated the predictive value of clinical/CT and cisternographic scales by assessing these with blinding to the results of other ancillary tests and to the postsurgical outcome. We tried to avoid a selection bias including all available cisternograms of all patients receiving shunts

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by

from 1980 to 1989; in addition, we calculated that the group of 75 patients was a representative sample of the total group, at least concerning distributions of clinical profile and postsurgical outcome. Taking further méthodologie limitations into account, our study confirmed not only that the predictive value of cisternography is low, but also that this test has no advantage over selecting patients for a shunt on the basis of combined clinical and CT data alone.

Hence,

1977;40:336-341. 15. Hughes CP, Siegel BA, Coxe WS,

et al. Adult idiopathic commu¬ nicating hydrocephalus with and without shunting. J Neurol Neurosurg Psychiatry. 1978;41:961-971. 16. Tans JTJ. Differentiation of normal pressure hydrocephalus and cerebral atrophy by computed tomography and spinal infusion test.

J Neurol. 1979;222:109-118.

17. Black PM. Idiopathic normal-pressure hydrocephalus: results of in 62 patients. J Neurosurg. 1980;53:371-377. 18. Borgesen SE, Westgard L, Cjerris F. Isotope cisternography and conductance to outflow in CSF in normal pressure hydrocephalus. Acta

shunting

Neurochir. 1981;57:67-73. 19. McComb JC. Recent research into the nature of cerebrospinal fluid formation and absorption. / Neurosurg. 1983;59:369-383. 20. Craff-Radford NR, Godersky JC, Jones MP. Variables predicting surgical outcome in symptomatic hydrocephalus in the elderly. Neu¬

in centers not having access to technically complex and invasive tests, cisternography does not ap¬ pear to be a clinically useful diagnostic procedure. Larsson et al13 recently reported on the merits of quantitative isotope cisternography, consisting of calculating the ratio of ventricular stasis of the isotope to the total amount of intracranial radioactivity, but this study still needs redu¬ plication by others. Cisternography will probably be abandoned, as diagnostic facilities have been expanded with magnetic resonance imaging, including quantitative assessment of CSF flow,39-40 measurements of periventric¬ ular water proton relaxation times,41 and the ventricular/ convexity CSF ratio.42 Validation by prospective studies with blind evaluation of MR patterns, however, is still needed. Some promising results with cerebral blood flow studies43 in detecting SR-NPH also await validation in

Scott, ed. Concepts in Neurosurgery: Hydrocephalus. Baltimore, Md: Williams & Wilkins; 1990;3:109-114. 23. Bret P, Chazal J. Chronic hydrocephalus of the adult. Neurochir¬

Our study suggests that, in the mean time, cisternog¬ raphy should no longer be performed, as it will not reduce the diagnostic uncertainty remaining after clinical and CT

1986;7:817-822. 28. Inaba Y, Hiratsuka H, Tsuyumu M,

even

other centers.

evaluation.

We thank all our colleagues from North-Holland, who permitted to study the medical records of their patients and provided addi¬ tional information. We are also indebted to Hans van Crevel, MD, and Jan Stam, MD, and Albert Hijdra, MD, for their critical comments. us

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Normal-pressure hydrocephalus. Is cisternography still useful in selecting patients for a shunt?

The clinical usefulness of cisternography in selecting patients with presumed normal-pressure hydrocephalus for shunting was investigated in 76 patien...
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