Journal of the Neurological Sciences, 1979, 41 : 175-181 © Elsevier/North-Holland Biomedical Press
175
BULBOCAVERNOSUS R E F L E X IN PATIENTS W I T H CONUS M E D U L L A R I S A N D C A U D A E Q U I N A LESIONS
CUMHUR ERTEK|N, FATiN REEL, RIFAT MUTLU and ISMA|L KERKI~KLO Department of Clinical Neurology, Medical School Hospital, Aegean University, Bornova, lzmir (Turkey)
(Received 14 September, 1978) (Accepted 16 November, 1978)
SUMMARY The clinical value and practical application of the electrically induced BC reflex was investigated in 40 patients with traumatic or compressive lesions of the conus medullaris or cauda equina. It was shown that the BC reflex was either absent or delayed depending upon the involvement of the sacral 2-4 spinal and radicular segments. The latency of the BC reflex was normal in patients with mainly epiconus and lumbar cord involvement. The loss of the BC reflex in the acute period of traumatic lesions was an adverse prognostic sign while the presence of the reflex whether or not delayed, indicated a more benign final outcome of sphincter and sexual reflex disturbances. In chronic progressive compression, the latency of BC reflex was often delayed.
INTRODUCTION It has recently been shown that the electrically induced bulbocavernosus (BC) reflex is useful in evaluating neurogenic bladder disorders as well as neurogenic sexual impotence in men (Ertekin and Reel 1976). Since the afferent input from the urogenital skin and mucosa and the efferent signals from the sacral cord are mainly conveyed by sacral spinal roots 2, 3 and 4, any lesion which involves the conus or cauda equina could be expected to produce abnormalities of the BC reflex which uses anatomophysiological circuits similar to those of the micturition and sexual reflexes (Lapides and Bobbitt 1956). Indeed, the BC reflex has been found to be either absent or to have a prolonged latency in 13 patients with cauda equina lesions (Ertekin and Reel 1976) Adress for correspondence and reprint requests: Prof. Dr. C. Ertekin, Department of Neurology, Medical School Hospital, Aegean University, Bornova, Izmir, Turkey.
176 In this paper, the clinical value and practical application of the BC reflex in 40 male patients having lesions of the conus or cauda equina will be described. MATERIAL AND METHODS Forty male adult patients were investigated. In the majority the clinical picture indicated conus medullaris or cauda equina involvement, the signs of an epiconus lesion (Guttmann 1976) being also present in 8 cases. However, some patients showed dissociated and incomplete involvement of the conus or cauda equina indicated by the type and distribution of the disorder of cutaneous sensation. The causes of the clinical picture were classified into 3 groups and shown in Table 1, together with their radiological localization determined either by direct X-rays of the thoraco-lumbar spine or by myelography. Of the patients with traumatic fracture/ dislocations of the lumbar spine, 8 were investigated during the first week to the first month after trauma and the investigation was repeated 2-11 months after the injury in 4. Similarly the investigation was performed twice in two cases of acute midline herniated nucleus pulposus. The patients with compression from tumours were examined either pre- or postoperatively and the results in 3 were compared in pre- and postoperative periods. In all cases needle E M G and nerve conduction velocities were studied in muscles and nerves of the leg, often bilaterally, allowing additional localization of radicular and spinal cord involvement.
TABLE 1 THE CAUSES OF CONUS AND CAUDA EQUINA LESIONS IN 40 PATIENTS INVESTIGATED X-ray localization (vertebral level) Th11 Th12 L1
L2
1 1
1
L3
L:t
L5
I -
~
L Traumatic" fracture/dislocation o f spine
(a) investigated in acute period (b) investigated in later period
1 1
4 9
1 1~
8 13
21 H. Midline herniatednucleuspulposas
(a) investigated in acute period (b) investigated in later period
2
--
-
2
3
1
-
4 6
III. Tumours
I
2
1
1
3
2
3
13
Total
3
4
14
2
10
4
3
40
a One case is included in this group with an acute cauda equina syndrome after spinal anesthesia for inguinal hernia operation.
177 The electrophysiological m e t h o d of eliciting the BC reflex as previously described (Ertekin and Reel 1976) was applied in all 40 patients. At the same time the BC muscle was evaluated electromyographically. The glans penis was stimulated superficially by single electrical pulses and the reflex E M G responses were recorded f r o m the BC muscle by means o f concentric needle electrodes. Since anesthesia or severe hypesthesia was present on the glans penis it was necessary to use rectangular electrical shocks o f 0.5 or 1.0 ms duration and 500 V intensity, and brief trains o f repetitive shocks at 100/s were applied in m a n y cases in order to evoke the reflex. The records o f patients were c o m p a r e d individually to those obtained from n o r m a l adult male subjects reported previously. The upper limit o f the latency of the BC reflex in n o r m a l subjects was calculated as the mean plus 2 standard deviations (36.1 -t- 9.2), i.e. 45.3 ms. The longest latency recorded in a normal subject was 42.5 ms (Ertekin and Reel 1976).
Fig. 1. BC reflex responses obtained by successive single stimuli at 1/s. A normal control of a 46-yearold male (left) and a patient of 49 years old with a cauda equina syndrome due to L2-a postero-median herniated nucleus pulposus (right). Calibration :_200 #V and 100 ms.
178 RESULTS In 40 patients, 53 examinations of the BC reflex were performed, the reflex response being absent in 26 examinations in 19 patients. On the other hand, the BC reflex was obtainable in 27 examinations of 21 patients. In these cases, the mean latency of the BC reflex was significantly prolonged (52 ms -4- 5.0, SD = 25.7) compared to normal values (36.1 ms -+- 1.2, SD = 4.6)(P -< 0.01). In 10 of the 21 patients in whom a BC reflex was obtained latency was normal. In the remaining patients there was a remarkable reflex delay with latencies up to 120-130 ms (Fig. 1). In addition to the reflex delay, fluctuation of the reflex latency was also prominent and sometimes it was necessary to evoke the reflex response by repetitive electrical shocks which would be painful for normal controls (Fig. 2). The size of the BC reflex was often diminished to a small motor unit especially in the acute period of the trauma but in epiconus involvement such responses could later change into very dense responses with after-discharges in which the latency of the BC reflex was almost always normal. The absence or delay of the BC reflex depended upon the involvement of the sacral 2-4 spinal/radicular segments. When the BC reflex could be evoked with normal latency the lesion was above the sacral segments as determined by the lack ofdenervation signs in E M G of the BC muscle which is innervated by sacral 2, 3 and 4 motor roots (Haymaker 1969; Guttmann 1976). In contrast, when signs of total denervation were found in the BC muscle, loss of the BC reflex was the main finding. Between these
ur~np~suu~qr~j~up~rq~luu~un~
,
- ~
~
-
Fig. 2. Ten superimposed BC reflex responses from a normal adult male of 21 years old (top) and a 52-year-old patient with a cauda equina syndrome which appeared after spinal anesthesia (bottom). A brief train of 100 Hz frequencywas used for the patient. Calibration: 10 ms in between two successive positive peaks and 150/~V from peak to peak.
179
Fig. 3. BC reflexes in a patient of 44 years old with fracture/dislocation of L1 vertebra. BC responses on the 20th day after trauma (top) and on the 60th day after trauma (bottom). Calibration: 50 ms and 30/~V (top), 300 #V (bottom).
k
Fig. 4. BC reflexes in a patient of 37 years old with an epidermoid cyst causing slowly a progressive cauda equina syndrome. Before (left) and 3 weeks after operative removal (right). Calibration: 100 ms and 400/~V.
180 extremes, the features of the BC reflex were variable. For instance if the E M G signs of partial denervation were found in the BC muscle, the BC reflex was either absent or evoked with a prolonged latency. However, the EMG of the BC muscle showed either absence of voluntary activity or reduction of motor unit potentials on voluntary effort in 8 patients. Such inconclusive E M G findings were especially found in the acute period of traumatic cases because it was too early for the appearance of signs of denervation. Therefore it was difficult to judge whether the sacral radicular motor segments were involved or whether the cessation of voluntary activity was due to upper motor neuron involvement. These 8 cases could only be evaluated by means of the BC reflex, which was either absent or present with very prolonged onset latency in 4 cases indicating important sacral spinal or radicular involvement. Abnormalities of the BC reflex were present in 60 ~ of acute spinal trauma; in 100 ~ in postero-median herniated nucleus pulposus and in 77 ~ in compression due to tumours, depending on the extent of the lower sacral root and cord involvement. The loss of the BC reflex was more frequent in acute spinal trauma while in the other two groups, there was sometimes remarkable delay in the reflex. Absence of the BC reflex in the acute period in the traumatic patients seemed to be important in regard to the final outcome, suggesting that the disturbances of bladder and sexual functions would not recover satisfactorily. On the other hand, the presence of the BC reflex, whether or not delayed, was more favorable for improvement in sexual and bladder functions, paralleling recovery of the BC reflex in later investigations (Fig. 3). Loss of the BC reflex was also found in patients with acute or subacute onset of compression of the conus and cauda equina region by tumours and herniated discs while prolonged reflex responses were more often recorded in slowly progressive compressive lesions. After removal of compression the BC reflex tended to appear with a shorter latency (Fig. 4). DISCUSSION Since the BC reflex indicates the integrity of sacral spinal segments 2, 3 and 4, and of their afferent and efferent connections in the urogenital region, pathological changes in the reflex would be expected in patients with lesions of the conus and cauda equina. Thus, severe involvement of the sacral radicular or spinal segments, especially in traumatic fracture/dislocation of the lumbar spine, resulted in the loss of the BC reflex and this finding seems to be very important in prognosis because in cases investigated in the acute or later stages both bladder and sexual dysfunction almost always accompanied loss of the BC reflex. Conversely, the presence of the BC reflex, either delayed or normal in latency, indicates more a favorable outcome for sexual and bladder functions. It is proposed that the loss of the BC reflex is the result of the disruption or severe crushing of the sacral radicular spinal nerves. This conclusion can be supported by the findings of E M G signs of total denervation in pelvic muscles including the BC muscle and in the leg muscles belonging mainly to sacral myotomes. Such a severe axonal degeneration could not be followed by any regeneration (Crosby et al. 1962).
181 Therefore, both absence of the BC reflex and the sexual and bladder dysfunction persist. I f the BC reflex could be evoked with a prolonged latency, as it was seen more frequently in compression by herniated discs or by tumours, another pathophysiological phenomenon may operate. Many of the afferent and efferent impulses carried by radicular nerves could be slowed at the site of compression. Slowing of conduction would increase if local demyelination developed especially in slowly progressive compression. Such local slowing is similar to that encountered in peripheral nerve entrapment neuropathies (Kaeser 1970; Gilliatt 1973). Local slowing in nerve roots has also been found during neurosurgical relief of lumbosacral disc compression (Granger and Flanigan 1968) and in the experimental model (Gelfan and Tarlov 1956). Furthermore, the onset latency of lumbosacral segmental evoked cord potentials recorded just above in cauda equina compressive lesions were found to be significantly prolonged (Ertekin 1978). A BC reflex with normal latency can be explained in the following way: the level of the anatomical lesion is above the sacral segments and the arc of the BC reflex is preserved and remains excitable, in spite of spinal shock, when examined in cases o f epiconus involvement as early as the first and second weeks after the injury. F r o m a practical point of view the BC reflex seems to be important in determining the degree and type of sacral spinal or radicular involvement and is also superior to needle E M G of the sacral segmental innervated muscles especially during the acute period of vertebral fracture/dislocations. It is also useful in foretelling the final outcome of sacral spinal functions in the early days of traumatic lesions and in comparing operative results in compressive lesions. REFERENCES Crosby, E. C., T. Humphrey and E. W. Laver (1962) Correlative Anatomy of the Nervous System, McMillan Comp., New York, NY. Ertekin, C. (1978) Evoked electrospinogram in spinal cord and peripheral nerve disorders, Acta neuroL scand., 57 : 329-344. Ertekin, C. and F. Reel (1976) Bulbocavernosus reflex in normal men and in patients with neurogenic bladder and/or impotence, J. neurol. Sci., 28: 1-15. Gelfan, S. and I. Tarlov (1956) Physiology of spinal cord, nerve root and peripheral nerve compression, Amer. J. Physiol., 185: 217-229. Gilliatt, R. W. (1973) Recent advances in the pathophysiology of nerve conduction. In : J. E. Desmedt (Ed.), New Developments in Electromyography and Clinical Neurophysiology, Vol. 2, Karger, Basel, pp. 2-18. Granger, C. V. and S. Flanigan (1968) Nerve root conduction studies during lumbar disc surgery, J. Neurosurg., 28: 439-444. Guttmann, L. (1976) Spinal Cord l n j u r i e s - Comprehensive Management and Research, 2nd edition, Blackwell, Oxford, London, Edinburgh, Melbourne. Haymaker, W. (1969) Bing's Local Diagnosis in Neurological Diseases, Mosby, St. Louis, MO. Kaeser, H. E. (1970) Nerve conduction velocity measurements. In: P. J. Vinken and G. W. Bruyn (Eds.), Handbook of Clinical Neurology, VoL 7 (Diseases of Nerves, Part 1), North-Holland, Amsterdam, pp. 116-196. Lapides, J. and J. M. Bobbitt (1956) Diagnostic value of bulbocavernosus reflex, J. Amer. reed. Ass., 162: 971-972. Truex, R. C. and M. B. Carpenter (1969) Human Neuroanatomy, 6th edition, Williams and Wilkins, Baltimore, MD.
175
BULBOCAVERNOSUS R E F L E X IN PATIENTS W I T H CONUS M E D U L L A R I S A N D C A U D A E Q U I N A LESIONS
CUMHUR ERTEK|N, FATiN REEL, RIFAT MUTLU and ISMA|L KERKI~KLO Department of Clinical Neurology, Medical School Hospital, Aegean University, Bornova, lzmir (Turkey)
(Received 14 September, 1978) (Accepted 16 November, 1978)
SUMMARY The clinical value and practical application of the electrically induced BC reflex was investigated in 40 patients with traumatic or compressive lesions of the conus medullaris or cauda equina. It was shown that the BC reflex was either absent or delayed depending upon the involvement of the sacral 2-4 spinal and radicular segments. The latency of the BC reflex was normal in patients with mainly epiconus and lumbar cord involvement. The loss of the BC reflex in the acute period of traumatic lesions was an adverse prognostic sign while the presence of the reflex whether or not delayed, indicated a more benign final outcome of sphincter and sexual reflex disturbances. In chronic progressive compression, the latency of BC reflex was often delayed.
INTRODUCTION It has recently been shown that the electrically induced bulbocavernosus (BC) reflex is useful in evaluating neurogenic bladder disorders as well as neurogenic sexual impotence in men (Ertekin and Reel 1976). Since the afferent input from the urogenital skin and mucosa and the efferent signals from the sacral cord are mainly conveyed by sacral spinal roots 2, 3 and 4, any lesion which involves the conus or cauda equina could be expected to produce abnormalities of the BC reflex which uses anatomophysiological circuits similar to those of the micturition and sexual reflexes (Lapides and Bobbitt 1956). Indeed, the BC reflex has been found to be either absent or to have a prolonged latency in 13 patients with cauda equina lesions (Ertekin and Reel 1976) Adress for correspondence and reprint requests: Prof. Dr. C. Ertekin, Department of Neurology, Medical School Hospital, Aegean University, Bornova, Izmir, Turkey.
176 In this paper, the clinical value and practical application of the BC reflex in 40 male patients having lesions of the conus or cauda equina will be described. MATERIAL AND METHODS Forty male adult patients were investigated. In the majority the clinical picture indicated conus medullaris or cauda equina involvement, the signs of an epiconus lesion (Guttmann 1976) being also present in 8 cases. However, some patients showed dissociated and incomplete involvement of the conus or cauda equina indicated by the type and distribution of the disorder of cutaneous sensation. The causes of the clinical picture were classified into 3 groups and shown in Table 1, together with their radiological localization determined either by direct X-rays of the thoraco-lumbar spine or by myelography. Of the patients with traumatic fracture/ dislocations of the lumbar spine, 8 were investigated during the first week to the first month after trauma and the investigation was repeated 2-11 months after the injury in 4. Similarly the investigation was performed twice in two cases of acute midline herniated nucleus pulposus. The patients with compression from tumours were examined either pre- or postoperatively and the results in 3 were compared in pre- and postoperative periods. In all cases needle E M G and nerve conduction velocities were studied in muscles and nerves of the leg, often bilaterally, allowing additional localization of radicular and spinal cord involvement.
TABLE 1 THE CAUSES OF CONUS AND CAUDA EQUINA LESIONS IN 40 PATIENTS INVESTIGATED X-ray localization (vertebral level) Th11 Th12 L1
L2
1 1
1
L3
L:t
L5
I -
~
L Traumatic" fracture/dislocation o f spine
(a) investigated in acute period (b) investigated in later period
1 1
4 9
1 1~
8 13
21 H. Midline herniatednucleuspulposas
(a) investigated in acute period (b) investigated in later period
2
--
-
2
3
1
-
4 6
III. Tumours
I
2
1
1
3
2
3
13
Total
3
4
14
2
10
4
3
40
a One case is included in this group with an acute cauda equina syndrome after spinal anesthesia for inguinal hernia operation.
177 The electrophysiological m e t h o d of eliciting the BC reflex as previously described (Ertekin and Reel 1976) was applied in all 40 patients. At the same time the BC muscle was evaluated electromyographically. The glans penis was stimulated superficially by single electrical pulses and the reflex E M G responses were recorded f r o m the BC muscle by means o f concentric needle electrodes. Since anesthesia or severe hypesthesia was present on the glans penis it was necessary to use rectangular electrical shocks o f 0.5 or 1.0 ms duration and 500 V intensity, and brief trains o f repetitive shocks at 100/s were applied in m a n y cases in order to evoke the reflex. The records o f patients were c o m p a r e d individually to those obtained from n o r m a l adult male subjects reported previously. The upper limit o f the latency of the BC reflex in n o r m a l subjects was calculated as the mean plus 2 standard deviations (36.1 -t- 9.2), i.e. 45.3 ms. The longest latency recorded in a normal subject was 42.5 ms (Ertekin and Reel 1976).
Fig. 1. BC reflex responses obtained by successive single stimuli at 1/s. A normal control of a 46-yearold male (left) and a patient of 49 years old with a cauda equina syndrome due to L2-a postero-median herniated nucleus pulposus (right). Calibration :_200 #V and 100 ms.
178 RESULTS In 40 patients, 53 examinations of the BC reflex were performed, the reflex response being absent in 26 examinations in 19 patients. On the other hand, the BC reflex was obtainable in 27 examinations of 21 patients. In these cases, the mean latency of the BC reflex was significantly prolonged (52 ms -4- 5.0, SD = 25.7) compared to normal values (36.1 ms -+- 1.2, SD = 4.6)(P -< 0.01). In 10 of the 21 patients in whom a BC reflex was obtained latency was normal. In the remaining patients there was a remarkable reflex delay with latencies up to 120-130 ms (Fig. 1). In addition to the reflex delay, fluctuation of the reflex latency was also prominent and sometimes it was necessary to evoke the reflex response by repetitive electrical shocks which would be painful for normal controls (Fig. 2). The size of the BC reflex was often diminished to a small motor unit especially in the acute period of the trauma but in epiconus involvement such responses could later change into very dense responses with after-discharges in which the latency of the BC reflex was almost always normal. The absence or delay of the BC reflex depended upon the involvement of the sacral 2-4 spinal/radicular segments. When the BC reflex could be evoked with normal latency the lesion was above the sacral segments as determined by the lack ofdenervation signs in E M G of the BC muscle which is innervated by sacral 2, 3 and 4 motor roots (Haymaker 1969; Guttmann 1976). In contrast, when signs of total denervation were found in the BC muscle, loss of the BC reflex was the main finding. Between these
ur~np~suu~qr~j~up~rq~luu~un~
,
- ~
~
-
Fig. 2. Ten superimposed BC reflex responses from a normal adult male of 21 years old (top) and a 52-year-old patient with a cauda equina syndrome which appeared after spinal anesthesia (bottom). A brief train of 100 Hz frequencywas used for the patient. Calibration: 10 ms in between two successive positive peaks and 150/~V from peak to peak.
179
Fig. 3. BC reflexes in a patient of 44 years old with fracture/dislocation of L1 vertebra. BC responses on the 20th day after trauma (top) and on the 60th day after trauma (bottom). Calibration: 50 ms and 30/~V (top), 300 #V (bottom).
k
Fig. 4. BC reflexes in a patient of 37 years old with an epidermoid cyst causing slowly a progressive cauda equina syndrome. Before (left) and 3 weeks after operative removal (right). Calibration: 100 ms and 400/~V.
180 extremes, the features of the BC reflex were variable. For instance if the E M G signs of partial denervation were found in the BC muscle, the BC reflex was either absent or evoked with a prolonged latency. However, the EMG of the BC muscle showed either absence of voluntary activity or reduction of motor unit potentials on voluntary effort in 8 patients. Such inconclusive E M G findings were especially found in the acute period of traumatic cases because it was too early for the appearance of signs of denervation. Therefore it was difficult to judge whether the sacral radicular motor segments were involved or whether the cessation of voluntary activity was due to upper motor neuron involvement. These 8 cases could only be evaluated by means of the BC reflex, which was either absent or present with very prolonged onset latency in 4 cases indicating important sacral spinal or radicular involvement. Abnormalities of the BC reflex were present in 60 ~ of acute spinal trauma; in 100 ~ in postero-median herniated nucleus pulposus and in 77 ~ in compression due to tumours, depending on the extent of the lower sacral root and cord involvement. The loss of the BC reflex was more frequent in acute spinal trauma while in the other two groups, there was sometimes remarkable delay in the reflex. Absence of the BC reflex in the acute period in the traumatic patients seemed to be important in regard to the final outcome, suggesting that the disturbances of bladder and sexual functions would not recover satisfactorily. On the other hand, the presence of the BC reflex, whether or not delayed, was more favorable for improvement in sexual and bladder functions, paralleling recovery of the BC reflex in later investigations (Fig. 3). Loss of the BC reflex was also found in patients with acute or subacute onset of compression of the conus and cauda equina region by tumours and herniated discs while prolonged reflex responses were more often recorded in slowly progressive compressive lesions. After removal of compression the BC reflex tended to appear with a shorter latency (Fig. 4). DISCUSSION Since the BC reflex indicates the integrity of sacral spinal segments 2, 3 and 4, and of their afferent and efferent connections in the urogenital region, pathological changes in the reflex would be expected in patients with lesions of the conus and cauda equina. Thus, severe involvement of the sacral radicular or spinal segments, especially in traumatic fracture/dislocation of the lumbar spine, resulted in the loss of the BC reflex and this finding seems to be very important in prognosis because in cases investigated in the acute or later stages both bladder and sexual dysfunction almost always accompanied loss of the BC reflex. Conversely, the presence of the BC reflex, either delayed or normal in latency, indicates more a favorable outcome for sexual and bladder functions. It is proposed that the loss of the BC reflex is the result of the disruption or severe crushing of the sacral radicular spinal nerves. This conclusion can be supported by the findings of E M G signs of total denervation in pelvic muscles including the BC muscle and in the leg muscles belonging mainly to sacral myotomes. Such a severe axonal degeneration could not be followed by any regeneration (Crosby et al. 1962).
181 Therefore, both absence of the BC reflex and the sexual and bladder dysfunction persist. I f the BC reflex could be evoked with a prolonged latency, as it was seen more frequently in compression by herniated discs or by tumours, another pathophysiological phenomenon may operate. Many of the afferent and efferent impulses carried by radicular nerves could be slowed at the site of compression. Slowing of conduction would increase if local demyelination developed especially in slowly progressive compression. Such local slowing is similar to that encountered in peripheral nerve entrapment neuropathies (Kaeser 1970; Gilliatt 1973). Local slowing in nerve roots has also been found during neurosurgical relief of lumbosacral disc compression (Granger and Flanigan 1968) and in the experimental model (Gelfan and Tarlov 1956). Furthermore, the onset latency of lumbosacral segmental evoked cord potentials recorded just above in cauda equina compressive lesions were found to be significantly prolonged (Ertekin 1978). A BC reflex with normal latency can be explained in the following way: the level of the anatomical lesion is above the sacral segments and the arc of the BC reflex is preserved and remains excitable, in spite of spinal shock, when examined in cases o f epiconus involvement as early as the first and second weeks after the injury. F r o m a practical point of view the BC reflex seems to be important in determining the degree and type of sacral spinal or radicular involvement and is also superior to needle E M G of the sacral segmental innervated muscles especially during the acute period of vertebral fracture/dislocations. It is also useful in foretelling the final outcome of sacral spinal functions in the early days of traumatic lesions and in comparing operative results in compressive lesions. REFERENCES Crosby, E. C., T. Humphrey and E. W. Laver (1962) Correlative Anatomy of the Nervous System, McMillan Comp., New York, NY. Ertekin, C. (1978) Evoked electrospinogram in spinal cord and peripheral nerve disorders, Acta neuroL scand., 57 : 329-344. Ertekin, C. and F. Reel (1976) Bulbocavernosus reflex in normal men and in patients with neurogenic bladder and/or impotence, J. neurol. Sci., 28: 1-15. Gelfan, S. and I. Tarlov (1956) Physiology of spinal cord, nerve root and peripheral nerve compression, Amer. J. Physiol., 185: 217-229. Gilliatt, R. W. (1973) Recent advances in the pathophysiology of nerve conduction. In : J. E. Desmedt (Ed.), New Developments in Electromyography and Clinical Neurophysiology, Vol. 2, Karger, Basel, pp. 2-18. Granger, C. V. and S. Flanigan (1968) Nerve root conduction studies during lumbar disc surgery, J. Neurosurg., 28: 439-444. Guttmann, L. (1976) Spinal Cord l n j u r i e s - Comprehensive Management and Research, 2nd edition, Blackwell, Oxford, London, Edinburgh, Melbourne. Haymaker, W. (1969) Bing's Local Diagnosis in Neurological Diseases, Mosby, St. Louis, MO. Kaeser, H. E. (1970) Nerve conduction velocity measurements. In: P. J. Vinken and G. W. Bruyn (Eds.), Handbook of Clinical Neurology, VoL 7 (Diseases of Nerves, Part 1), North-Holland, Amsterdam, pp. 116-196. Lapides, J. and J. M. Bobbitt (1956) Diagnostic value of bulbocavernosus reflex, J. Amer. reed. Ass., 162: 971-972. Truex, R. C. and M. B. Carpenter (1969) Human Neuroanatomy, 6th edition, Williams and Wilkins, Baltimore, MD.
