[Spinal intramedullary tumors. When is surgical treatment indicated?]. / Spinale intramedulläre Tumoren Wann ist die operative Behandlung angezeigt?

OBJECTIVE: Timing of surgery in patients with intramedullary tumors is the subject of controversy. The aim of this retrospective study is to evaluate whether patients with intramedullary ependymomas and astrocytomas have a better postoperative prognosis without or with slight preoperative deficits than those with severe preoperative neurological disturbances. PATIENTS AND METHODS: During a period of 8.5 years (January 1992-August 2000), 34 patients with intramedullary tumors underwent surgery in our Neurosurgical Department. Among them there were five astrocytomas WHO grade II and ten ependymomas WHO grade II. Recurrences were observed in two patients with astrocytomas and one patient with ependymoma. Pre- and postoperative functional performance was classified according to the McCormick scale in grade I-IV (grade I: neurologically normal or mild focal deficit and grade IV: severe neurological deficits and without functional independence). The follow-up period varied from 4 to 76 months (mean: 27.9 months). RESULTS: All seven grade I patients remained unchanged after surgery. Two of four grade II patients improved to grade I; two deteriorated to grade III. Two of three grade III and IV patients remained unchanged and another one deteriorated from grade III to IV. CONCLUSION: At the best, intramedullary astrocytomas and ependymomas should be operated when symptoms are mild. Early surgery can achieve good functional outcome.

Concepts of combined endovascular and surgical treatment for dural arteriovenous fistulae: concepts derived from experience in treating three unusual lesions.

BACKGROUND: We describe a treatment protocol for patients who have a dural arteriovenous fistulae (dAVF) not curable solely by an endovascular approach. MATERIAL AND METHODS: Three patients suffering from neurological impairment due to a complex dAVM (intracranial haemorrhage 2, intracranial hypertension 1) were treated by a combination of arterial embolization treatment and subsequent surgery. RESULTS: Marked reduction of flow was achieved by embolization of the main arterial feeders of the fistulae. Surgery eliminated the residual dAVFs completely and without permanent morbidity. CONCLUSION: It is necessary to eliminate a dural fistula completely, especially in a patient whose fistula had drainage or reflux into cortical veins, which have a high risk of intracranial haemorrhage and venous hypertension. We present an approach to treatment using transarterial embolization and early surgery which may offer a safe and effective way to achieve complete elimination of the lesion, avoiding increased risk to important venous drainage.

Approach-related complications of transthoracic spinal reconstruction procedures.

Direct surgical repair of instabilities of the anterior spinal column has gained in importance. New techniques and instruments have led to better operative results. Inspite of the growing number of interventions at the anterior spinal column only little data is available on the typical intra- and postoperative complications of these anterior approaches Between 4/1998 and 8/2002, 85 patients in two neurosurgical centres were treated using an anterolateral transthoracic approach for various lesions of the thoracic and thoracolumbar spine. We used a minithoracotomy with video-endoscopic guidance in 75 of these patients. Intra- and postoperative complications were evaluated retrospectively. Two operations had to be abandoned, in all other cases surgery was performed as planned. Postoperatively, eleven patients complained of temporary intercostal neuralgia (12.9%), two patients (2.3%) had a pulmonary insufficiency which was treated conservatively, another patient needed drainage of a pleural effusion. One intraoperative injury to the thoracic duct was treated conservatively, one hernia of the abdominal wall had to be corrected surgically. Relevant injuries to the vessels did not occur, blood loss was 520 ml on average. There was no surgical mortality; one revision surgery had to be performed because of bone graft dislocation. The rate of severe approach-related complications was 4/85 = 4.7% (two abandoned procedures, one injury to the thoracic duct, one abdominal hernia). Transthoracic anterolateral stabilisation via a minithoracotomy with video-endoscopic guidance is an effective surgical approach to treat instabilities of the anterior parts of the thoracic spine and the thoracolumbar area with low complication rates.

Atlantoaxial screw fixation for the treatment of isolated and combined unstable jefferson fractures - experiences with 8 patients.

The unstable atlas burst fracture ("Jefferson fracture") is a fracture of the anterior and posterior atlantal arch with rupture of the transverse atlantal ligament and an incongruence of the atlanto-occipital and the atlanto-axial joint facets. The question whether it has to be treated surgically or nonsurgically is still discussed and remains controversial. During the last decade 8 patients with unstable atlas burst fractures were examined and treated in our department. Five of the eight patients were first treated conservatively by external immobilization. Because of continuing instability due to insufficient bony fusion of the atlantal fracture all five patients underwent atlanto-axial transarticular screw fixation and fusion - as described by Magerl - with good results. In all 8 patients a good bony fusion of the atlanto-axial segment was achieved. None of the patients exhibited neurological deficits after surgical treatment. Although immobilization with a halo vest is recommended by most authors, from our view primary transarticular C1-C2 screw fixation has to be discussed as an alternative for unstable atlas burst fractures. Nonsurgical treatment with halo extension always bears the risk of insufficient healing with further instability and a fixated incongruence of the atlanto-occipital and the atlanto-axial joints, leading to arthrosis, immobility and increasing neck pain. After 10 weeks of insufficient immobilization secondary pre- and intra-operative reposition manoeuvres and surgical fixation hardly can reverse this fixated incongruence. Moreover, halo-extension needs an immobilization of the cervical spine for about 10 weeks and more, which is very uncomfortable and leads to further complications especially in elderly patients.

In vivo experiences with frameless stereotactically guided screw placement in the spine--results from 75 consecutive cases.

Whereas cranial neuronavigation is widely accepted as a helpful tool, larger series of the in vivo application of spinal neuronavigation do not exist. In the following we report our 4-year experience with spinal navigation in 75 consecutive cases for dorsal transpedicular screw placement. Seventy-five patients were planned for operation employing anatomical reference points defined on a 2-mm high resolution CT. We used single vertebra registration and surface matching. With the above methods, the mean registration deviation ranged from 0.18 mm (cervical spine) to 0.31 mm (lumbar spine). All our screws in the upper cervical spine were navigated correctly (17 patients), thus improving markedly the surgical outcome. The results were not as promising in the lumbar area. In only 84% was navigation reliable. The reason was the lack of a practicable tracking tool. Spinal neuronavigation based on anatomical reference points is able to improve the results in transpedicular screwing, especially in the cervical spine. The lack of a practicable tracking tool still hinders its use in routine clinical application.

Evaluation of iatrogenic lesions in 722 surgically treated cases of peripheral nerve trauma.

OBJECT: The purpose of this study was to discover the number and types of iatrogenic nerve injuries that were surgically treated during a 9-year period at a relatively busy nerve center. The specific nerves involved, their sites of injury, and the mechanisms of injury were also documented. METHODS: The authors retrospectively evaluated the surgically treated iatrogenic lesions by reviewing case histories, operative reports, and follow-up notes in 722 cases of trauma. These cases were treated between January 1990 and December 1998 because of pain, dysesthesias, and sensory and/or motor deficits. latrogenic injury was a much larger category of trauma than predicted. One hundred twenty-six (17.4%) of the 722 surgically treated cases were iatrogenic in origin. Most of these injuries occurred during a previous operation. To a major extent, nerves of the extremities were affected, and a relatively large number of injuries occurred in the neck and groin. Incidence was highest in the spinal accessory nerve (14 cases), the common peroneal nerve (11 cases), the superficial radial nerve (10 cases), the genitofemoral nerve branches (10 cases), and the median nerve (nine cases). At least two thirds of the patients did not undergo surgery for the iatrogenic injury within an optimal time interval due to delayed referral. Follow-up data were available in 97 of the 126 patients. Surgical outcomes demonstrated improvement in 70% of patients. Operative results were especially favorable in patients suffering from iatrogenic injuries to the accessory and superficial sensory radial nerves. CONCLUSIONS: latrogenic injuries should be corrected in a timely fashion just like any other traumatic injury to nerve.

[Compartment syndrome of the thigh with sciatic nerve paralysis]. / Das Kompartmentsyndrom am Oberschenkel mit Ischiadikusparese.

UNLABELLED: Acute compartment syndrome of the thigh has been infrequently reported in the literature. Closed femoral fractures and blunt soft tissue trauma are the main causes of this injury. The multiple injured patient in this case report developed a compartment syndrome of the thigh after intramedullary nailing of a comminuted fracture of the femur. Fasciotomy was performed two days after surgery because of extense swelling of the thigh in the ventilated and sedated patient. Sciatic and femoral nerve palsy was recognized after extubation of the patient nine days after the injury. During the following weeks the paresis of the femoral nerve recovered but neither motor nor sensory function of the sciatic nerve could be demonstrated. Therefore an operative revision of the sciatic nerve was performed eighteen weeks after trauma. No direct nerve injury could be detected but there were adhesions around the nerve as a sign of compression neuropathy caused by the compartment syndrome. The tibial component of the sciatic nerve showed a complete recovery within the next months but there was a persisting peroneal nerve palsy. CONCLUSION: Early clinical symptoms of a compartment syndrome like pain, paresthesia and paresis can not be ascertained in a ventilated and sedated patient. Tense swelling of the muscles is often the only detectable sign. Frequent measurements of compartment pressure should be done in these patients. We suggest early decompressive fasciotomy because the morbidity caused by fasciotomy in a borderline compartment syndrome is far outweighed by the morbidity that accompanies an undiagnosed untreated compartment syndrome with possible nerve palsy.

Radiological investigations and intra-operative evoked potentials for the diagnosis of nerve root avulsion: evaluation of both modalities by intradural root inspection.

Fourteen patients with traumatic brachial plexus injuries underwent intradural inspection of cervical nerve roots to evaluate radiological and intra-operative electrophysiological findings concerning cervical nerve root avulsion from the spinal cord. Four neurosurgeons of our department assessed independently from each other both myelography and CT-myelography concerning intradural nerve root lesions. Each neurosurgeon assessed a total of 26 cervical nerve roots. Two investigators assessed 6/26 and 2 investigators 7/26 nerve roots falsely concerning ventral or/and dorsal root lesions compared with the findings on intradural inspection (23% and 27% false findings). There was a considerable variance concerning the assessibility and findings among the 4 neurosurgeons. Reconstructive surgery was performed after a mean interval of 6.5 months following trauma and 2 weeks following intradural inspection. After exposure of the brachial plexus and the cervical nerve roots in question via a ventral approach, 13 cervical nerve roots were stimulated electrically close to the neuroforamen and cortical evoked potentials (root-SEPs) were recorded from the contralateral postcentral region. All 5 roots with SEPs were intact (no root lesion) and all 8 roots without SEPs showed interrupted (ventral or/and dorsal) rootlets on intradural inspection. Our results demonstrate that false radiological findings concerning root lesions are possible. Intra-operative root-SEPs seem to be a useful aid for evaluation of cervical nerve root lesions. However, more electrophysiological data are necessary to ascertain, if this modality is able to replace intradural inspection in unclear radiological cases in the future.

Laminar and arch fractures with dural tear and nerve root entrapment in patients operated upon for thoracic and lumbar spine injuries.

OBJECTIVE: To determine the neurological outcome in patients with laminar fractures associated with dural tears and nerve root entrapment, operated upon for thoracic and lumbar spine injuries. PATIENT POPULATION: Out of 103 patients operated upon consecutively for thoracic and lumbar spine injuries during the period 1990 to 1994 inclusive, 24 (23.3%) patients had laminar fractures out of whom 3 (2.9%) had an associated dural tear and an other 17 (16.5% or 70.8% of the total patients with laminar fractures) had an associated dural tear and nerve root entrapment. RESULTS: Twelve (70.5%) patients had injury at the thoraculumbar junction, 13 (76.5%) had Magerl's type A3 or above, 10 (58.8%) had a kyphotic angle deformity greater than 5 degrees. Seven (41.1%) had their spinal canal's sagittal diameter reduced by at least 50% and two had dislocations. Nine (52.9%) had initial neurological deficits. Four (50%) out of 8 patients with no initial neurological deficits (Frankel E) worsened to Frankel D. However, one patient among the 3 with initial Frankel A improved to Frankel C while both patients with initial Frankel C usefully improved to final Frankel grades D and E respectively. Two of the four patients with initial Frankel D improved to Frankel E, the other 2 remaining unchanged. All in all five patients neurological status improved, 4 worsened and 8 remained unchanged after neurosurgical treatment. CONCLUSIONS: Vertical laminar fractures with dural tears and nerve root entrapment represent a special group of thoracic and lumbar spine injuries that carry a poor prognosis. However, special operative precautions lead to significant improvement in some of them although a majority remain unchanged or even worsened.

Value of nerve action potentials in the surgical management of traumatic nerve lesions.

OBJECTIVE: The goals of the study were to investigate the value of intraoperative electrically evoked nerve action potentials (NAPs) in the surgical treatment of traumatic peripheral nerve injuries (nerve lesions in continuity). METHODS: Sixty-four patients with 76 traumatic nerve lesions in continuity were investigated intraoperatively by stimulating and recording NAP from the whole nerve across the suspected lesion site. Among the 76 nerves (nerve lesions) were 43 with incomplete and 33 with complete loss of function. In cases (nerves) with complete loss of function (n = 33), the surgical procedure (external neurolysis, internal neurolysis, or nerve repair) was performed according to the microscopic aspect of the nerve and the result of the intraoperative electrophysiological testing. In cases (nerves) with incomplete loss of function (n = 43), the surgical procedure was performed solely according to the microscopic aspect of the nerve and independently from the result of the intraoperative electrophysiological testing. RESULTS: Of 43 nerves with incomplete loss of function, we were able to record reproducible NAPs in 41 (95%) across the lesion site, thus demonstrating a high reliability of the method. Of 33 nerves with complete loss of function, a reproducible NAP could be recorded only in 3. Assuming an axonotmetic lesion in regeneration, we did nothing else on the nerve with excellent clinical results (full recovery). Of the remaining nerves with no NAP, 24 showed a caliber shift of the nerve (in 20 cases a thickening of the nerve, suggesting a neuroma in continuity). A grafting procedure was performed, and the histological evaluation revealed a neurotmetic lesion. However, in six patients with no NAP, there was no clear caliber shift of the nerve. The epineurium was opened and an internal neurolysis performed showing fascicles in continuity. Three patients had good and three had partial (but useful) recovery. CONCLUSIONS: In nerve lesions in continuity with complete loss of nerve function, intraoperative NAPs are able to detect axonotmetic lesions in regeneration. Thus, unnecessary further surgical procedures can be avoided. On the other end of the spectrum, no recordable NAP together with a caliber shift of the nerve (suggesting a neuroma in continuity) may facilitate the surgeon's decision for a grafting procedure without a time-consuming internal neurolysis. But there is also evidence from our data that not every nerve lesion in continuity without a NAP needs to be grafted.

[Experiences with endoscopic surgery in treatment of carpal tunnel syndrome. Preliminary results of a prospective study]. / Erfahrungen mit der endoskopischen Operation zur Behandlung des Karpaltunnelsyndroms. Vorläufige Ergebnisse einer prospektiven Studie.

Endoscopic carpal tunnel release is a new technique for treatment of carpal tunnel syndrome. The benefits of this procedure are a small skin wound with less local pain, the fact that the hand can quickly be used again, and earlier return to work or other activities. We present the preliminary results of the 3-month follow-up of 88 patients out of a prospective study of 100 patients. All patients were operated on using the one-port technique. Six additional decompressions had to be abandoned and open release was performed. Of the patients with pain, 73.6% (68/88) were completely pain-free and in 13.2% (9/68) pain improved in more than 50%. Subjective symptoms like paresthesia and numbness of the hand disappeared completely in 77.2% (64/83). Sensory deficits disappeared in 50% (33/66). Ten of 17 patients with preoperative paresis of the abductor pollicis brevis muscle and 11/14 with paresis of the opponens pollicis muscle had normal motor function 3 months after the operation. The complication rate concerning nerve lesions was 2.3%. The return to work time was 21 days (range 3-49 days). According to clinical symptoms, our preliminary results do not seem to have any benefits compared to the conventional open technique, and the costs for the endoscopic procedure are markedly higher. The complication rate after the learning curve period is approximately the same as open carpal tunnel release.

DREZ coagulations for deafferentation pain related to spinal and peripheral nerve lesions: indication and results of 79 consecutive procedures.

During a 16 years' period, a total of 79 dorsal root entry zone coagulations were performed in 68 patients for deafferentation pain. Of the 23 patients who underwent surgery for pain due to cervical root avulsion, 18 (82%) had a good (12) or fair (6) pain relief (mean follow-up period 51 months). Twelve (57%) patients with spinal cord injuries noted continuous pain reduction (10 good, 2 fair; mean follow-up 52 months). Continuous marked improvement for longer periods was reported only by 2 out of 10 patients with postherpetic neuralgia and 1 out of 7 patients with painful states due to other brachial plexus lesions and none out of 5 with spinal cord lesions (3) and phantom limb pain (2).

[Significance of distal motor latency after carpal tunnel operation]. / Zur Bedeutung der distalen motorischen Latenz nach Karpaltunneloperationen.

Motor distal latency (MDL) is one of the most important parameters in the electrodiagnosis of carpal tunnel syndrome (CTS). In a retrospective study of 1816 open surgical decompressions for CTS, a total of 612 postoperative motor nerve conduction measurements on 485 hands could be evaluated. In patients with good or satisfactory results after carpal tunnel release, an average improvement of MDL of 1.0 ms after 9-13 days, and of 2.2 ms after 1 year and longer was found. The individual motor nerve conduction improvement was in close correlation with the extent of preoperative prolongation of the MDL. Whereas relief of symptoms can be noted almost immediately, prolonged latencies often do not return to normal, even when the study is done a year later. Of the 10 patients with persisting symptoms, four had a new postoperative impairment of MDL, and also four had a marked improvement, whereas it remained unchanged in two. Patients with severe recurrent CTS presented in 11 out of 31 cases with an improved MDL from 0.3 ms to 3.0 ms in comparison to the initial preoperative evaluation; in 6 hands MDL was unchanged, further prolongation up to 2.0 ms was seen in 6 cases and marked worsening with new loss of motor response had to be noted in 8 hands at repeat electrodiagnosis. In 33 cases of postoperative reflex sympathetic dystrophy, an improvement of MDL from 0.3 ms to 3.3 ms (mean 1.7 ms) was observed in 22 hands and dissolution of a preexisting motor conduction block in three others, whereas two remained unchanged (without motor response) and an electrophysiological impairment was found only in six hands. Three of them presented with a further prolongation of MDL from 0.3 to 1.0 ms and a new loss of response was noted in the remaining three. In conclusion, postoperative motor nerve conduction studies may assess a favorable course following carpal tunnel release. However, they are often not helpful when surgical results are unsatisfactory, and indication for repeat surgical decompression should be based merely on clinical symptoms.

Findings and long-term results of subsequent operations after failed microvascular decompression for trigeminal neuralgia.

OBJECTIVE: To evaluate the indication of subsequent operations after failed microvascular decompression (MVD) for the treatment of trigeminal neuralgia, the intraoperative findings and long-term results of 16 subsequent operations are reported. METHODS: Subsequent exploration of the posterior fossa was performed for lack of pain relief (3 patients) and recurrent neuralgia (13 patients) after an average of 17 months (range, 4-62 mo). In all patients, typical arterial compression patterns at the root entry zone of the trigeminal nerve were found in the first procedure. The mean follow-up period after subsequent operation was 90 months (range, 78-104 mo). RESULTS: New arterial neurovascular conflicts were found in nine patients. After subsequent MVD procedures, seven patients were pain-free (with one recurrence after 6 mo), one had constant marked relief, and one was unchanged. Second exploration revealed no abnormalities in the other seven patients who experienced continued or recurrent pain; only careful neurolysis of the trigeminal nerve was performed in those patients. Initially, all seven patients obtained complete pain relief, but two experienced late recurrences after 64 and 68 months, respectively. Thus, subsequent operations failed in all 4 patients who had undergone prior destructive procedures but were successful in those 12 patients who had undergone only previous MVD. Two patients developed severe sequelae, and the other nine had minor complications, especially permanent (four patients) or transitory (three patients) ipsilateral trigeminal hypoesthesia. CONCLUSION: Subsequent MVD seems to have good long-term results. However, because of the significantly high incidence of complications, the indication for subsequent operations should be restricted to younger patients to avoid destructive procedures. In general, glycerol rhizolysis or radiofrequency rhizotomy may be the treatment of choice after failed MVD.

Neurosurgical management of thoracic and lumbar vertebral osteomyelitis and discitis in adults: a review of 43 consecutive surgically treated patients.

We report 43 consecutive surgically treated patients with pyogenic (37 patients) and tuberculous (6 patients) osteomyelitis of the thoracic and lumbar spine encountered within an 8-year period, including 1 with late recurrence after 15 months. There were 24 men and 18 women, ranging in age from 21 to 83 years. Twenty-six patients were in poor general condition because of associated illnesses, especially diabetes mellitus. Disease occurred at the thoracic level in 19 patients and on the lumbar spine in 24. After diagnosis, five patients were merely treated by posterior decompression; three of them, however, required further surgery for recurrent infection, spinal instability, and secondary neurological impairment. They are included in the 40 patients who underwent combined posterior débridement and internal fixation with transpedicular screw-rod systems. Autologous interbody bone grafting was performed simultaneously in 18 patients and in a second stage operation in 21 patients. One of them (tuberculous) experienced early recurrence and required anterior fusion. In two patients, methylmethacrylate packing was used for spine reconstruction; one of them had a late recurrence. Of the 26 patients with preoperative marked or severe neurological deficit (Frankel Grades A, 2 patients; B, 1 patient; C, 17 patients; and D, 6 patients), 23 (88%) had significant improvement of one grade (15 patients) or more (8 patients). There were no permanent complications. However, intensive care treatment was necessary in 20 of the 26 patients in reduced general condition (mean age, 72 yr). Two patients required further surgery because of postoperative epidural hematoma and pedicle screw malpositioning. In conclusion, most patients with thoracic and lumbar osteomyelitis can be successfully treated by combined débridement and internal fixation using only a posterior approach. Autogenous interbody bone grafting can be simultaneously performed and allows early mobilization of the patient.

Results of DREZ coagulations for pain related to plexus lesions, spinal cord injuries and postherpetic neuralgia.

The results of 58 dorsal root entry zone (DREZ) thermocoagulation procedures in 51 patients are reported. The postoperative analgesic effect was judged by the patients as being good (more than 75% pain reduction), fair (25-75% pain reduction) or poor (less than 25% pain reduction). Of the 14 patients who underwent surgery for pain due to cervical root avulsion, 10 (77%) had permanently good (8) or fair (2) pain relief after a mean follow up period of 76 months, another 2 (15%) experienced recurrence to the preoperative level (initially 1 good, 1 fair) after more than 2 and 4 years, respectively. Twenty two paraplegics were operated upon, 3 of whom twice, for intractable pain. After a mean observation time of 54 months, continuing pain relief was reported by 12 (55%) patients (11 good, 1 fair), and one (initially fair) had recurrent pain after 8 months. All 3 (early) re-operations remain successful for an average period of 75 months. Poor results were seen especially in cases of associated spinal cord cysts (5 out of 7), despite combined drainage, and in patients with diffuse pain distribution (5 out of 6). Continuous marked improvement for longer periods (mean follow up: 52 months) after DREZ lesions was reported only by 2 out of 10 patients with postherpetic neuralgia (12 procedures) and by 1 out of 5 with painful states due to radiation-induced brachial plexopathy (2), previous surgery (2) and malignant tumour infiltration of the brachial plexus (1). Three patients died postoperatively due to acute cardiac failure (2) and pulmonary embolism (1). Major complications, especially permanent gait disturbances were observed in 6 patients (12%) following primary procedures and in 2 out of 7 patients after re-operations, most of them suffering from postherpetic neuralgia. Minor neurological deficits were noted in 9 cases (18%). DREZ lesions revealed to be an effective procedure in patients with pain related to root avulsion and paraplegia. In contrast, it seems to be less successful for painful states due to other plexus lesions or postherpetic neuralgia.

[Intraoperative electrically evoked nerve action potentials in ulnar entrapment syndrome]. / Intraoperativ elektrisch evozierte Nervenaktionspotentiale beim Ulnarisrinnensydrom.

Many attempts have been made in the past to find predictive factors concerning patients operated on because of ulnar nerve entrapment at the elbow. The factors most frequently discussed in the literature are the patient's age, the importance of the preoperative neurological deficit, the duration of symptoms, accompanying diseases as diabetes mellitus or alcoholism and preoperative electrophysiological findings (EMG and conduction velocity measurements). With the exception of the electrophysiological findings, which uniformly are considered to be without predictive value, all other factors mentioned above are discussed controversly. In 1972 Kline and Nulsen [12] have shown, that intraoperatively evoked nerve action potentials across a traumatic nerve lesion can provide information about nerve regeneration. This information helps to choose the appropriate surgical procedure namely either neurolysis or neuroma resection and grafting. However there are no reports dealing with this method in nerve entrapment syndromes. We present the results of 17 patients with ulnar nerve entrapment at the elbow. They were operated on in our hospital between 1989 and 1992 by simple decompression or by anterior transposition of the nerve. In each of them we tried to record electrically evoked nerve action potentials intraoperatively and compared preoperative clinical findings with the potentials recorded. Our main interest was to find out, if the potentials have any predictive value regarding the clinical outcome. In 16 of 17 patients we were able to record a reproducable nerve action potential. Amplitudes varied between 3.4 and 140 uV. Conduction velocities of the fastest fibers ranged from 17 to 71 m/s, while potential duration varied between 1.3 to more than 8 ms.(ABSTRACT TRUNCATED AT 250 WORDS)