Electrophysiological improvement following decompression surgery in tarsal tunnel syndrome

Plantar nerve conduction studies 14 months to 3.5 years after decompression surgery in 3 cases of tarsal tunnel syndrome showed an improvement in motor conduction as well as in sensory nerve conduction. This electrophysiological improvement was associated with clinical improvement. However, minor abnormalities still existed in sensory nerve conduction in all 3 cases.     

Frequency-dependent conduction block in carpal tunnel syndrome

Frequency-dependent conduction block (FDB) across segments of demyelination in response to high-frequency nerve stimulation has been well demonstrated in animals and has been explored in humans. However, attempts to demonstrate this phenomenon in sensory fibers involved in entrapment neuropathies have been unsuccessful. Therefore, we investigated the effects of high-frequency nerve stimulation in the median motor nerve in patients with carpal tunnel syndrome (CTS) with moderate to severely increased distal motor terminal latencies (MTL). As a group, the mean decrease in negative peak amplitude (npAmp) during 20 stimuli at 30-HZ frequency was significantly greater in CTS subjects (-11.3%) than in controls (+7.9%). The degree of FDB was greater when MTL was more prolonged (i.e., -4.9% at 5.0 ms and -25.3% at 9.4 ms) and FDB was more pronounced at higher stimulation frequencies (20 and 30 HZ). Our results suggest that the safety margin for impulse transmission is impaired in the motor axons of patients with a focal demyelinating lesion. These findings may correlate with the observation of weakness in the absence of conduction block in patients with entrapment neuropathies.     

Focal conduction block in n-hexane polyneuropathy

A 19-year-old man with an asymptomatic history of recreational gasoline vapor inhalation presented with subacute progressive quadriparesis. For 2 weeks, he had intensely inhaled Coleman® fuel oil vapor, which contains n-hexane. Nerve conduction studies including near-nerve needle stimulation showed focal conduction block in the bilateral median and ulnar nerves. Sural nerve biopsy was consistent with giant axonal neuropathy. Conduction block as seen in this case has not heretofore been described in n-hexane polyneuropathy. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:964–969, 1998.     

Nerve ultrasound in electrophysiologically verified tarsal tunnel syndrome

Introduction: Tarsal tunnel syndrome (TTS) arises from tibial nerve damage under the flexor retinaculum of the fibro‐osseus tunnel at the medial malleolus. It is notoriously difficult to diagnose, as many other foot pathologies result in a similar clinical picture. We examined the additional value of nerve ultrasound in patients with tarsal tunnel syndrome confirmed by nerve conduction. Methods: We performed a retrospective analysis of nerve ultrasound changes in electrophysiologically confirmed TTS spanning our records from 2007 to 2015. Results: Nine feet with TTS were identified, all of which showed abnormal nerve ultrasound findings, which in 6 feet, led to identification of the underlying cause. Conclusions: This study shows that nerve ultrasound is abnormal in all cases of electrophysiologically verified TTS. The pattern of nerve abnormality is varied. This, and the fact that in the majority of patients causation was identified, suggests nerve ultrasound should form part of standard work‐up for TTS. Muscle Nerve 53 : 906–912, 2016     

AAEM case report #2: The carpal tunnel syndrome

The symptoms and sings which constitute the carpal tunnel syndrome (CTS) result from entrapment or compression of the median nerve within the carpal tunnel. Electrodiagnostic studies may objectively document the presence of median neuropathy within the carpal tunnel and help distinguish CTS from other disorders such as cervical radiculopathy, neurogenic thoracic outlet syndrome, proximal median nerve compression syndromes, and polyneuropathy which may either mimic or occasionally coexist with CTS. Recording median nerve responses with wrist and palm stimulation allows determination of the wrist segment conduction velocity which is a more sensitive nerve conduction parameter than wrist latency measurements. Electrodiagnostic testing permits estimation of severity and relative contribution of axonal versus demyelinative nerve injury. This information can provide prognostic information and help guide therapeutic decisions. © 1995 Mark A. Ross, MD and Jun Kimura, MD. Published John Wiley & Sons, Inc.     

Usefulness of electrodiagnostic techniques in the evaluation of suspected tarsal tunnel syndrome: an evidence-based review

This evidence-based review was performed to evaluate the utility of nerve conduction studies (NCSs) and needle electromyography (EMG) in the diagnosis of tibial neuropathy at the ankle (tarsal tunnel syndrome, TTS). A total of 317 articles on TTS were identified that were published in English from 1965 through April 2002, from the National Library of Medicine MEDLINE database. All articles were reviewed on the basis of six selection criteria. The results of this search revealed that four articles met five or more criteria. All four articles examined the use of electrodiagnostic (EDX) techniques for the evaluation of patients with clinically suspected TTS, and were included in this practice parameter. Each of these four studies was considered to meet Class III level of evidence. NCSs were abnormal in some patients with suspected TTS. Sensory NCSs were more likely to be abnormal than motor NCSs but the actual sensitivity and specificity could not be determined. The sensitivity of needle EMG abnormalities could not be determined. NCSs may be useful for confirming the diagnosis of tibial neuropathy at the ankle, recommendation Level C. Well-designed studies are needed to evaluate more definitively EDX techniques in TTS.     

The anterior tarsal tunnel syndrome

Summary The anterior tarsal tunnel syndrome, first described in 1968 by Marinacci, is characterized by a compression of the deep peroneal nerve under the inferior extensor retinaculum. The patients complaint of pains on the dorsum of the foot, especially at night. Clinically result sensory deficits in the involved area between the first and second toes as well as paresis and atrophy of the extensor digitorum brevis. The distal latency of the deep peroneal nerve is increased, the EMG shows active and chronic denervation of the extensor digitorum brevis. In cases with partial anterior tarsal tunnel syndrome only the motoric branch to the extensor digitorum brevis or only the sensory branch of the deep peroneal nerve after the division under the inferior extensor retinaculum is compressed. Two cases with complete and one with partial anterior tarsal tunnel syndrome are presented, etiology, symptomatology, differential diagnosis and therapeutic possibilities are discussed.

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Zusammenfassung Das 1968 erstmals von Marinacci beschriebene vordere Tarsaltunnelsyndrom besteht in einer Kompression des N. peronaeus profundus unter dem Ligamentum cruciatum. Subjektiv werden heftige, vor allem nachts auftretende Schmerzen im Fußrückenbereich geklagt. Klinisch resultieren sensible Ausfallserscheinungen im entsprechenden Hautareal zwischen der ersten und zweiten Zehe sowie Parese und Atrophie des M. extensor digitorum brevis. Elektroneurographisch findet sich eine erhöhte distale motorische Latenz des N. peronaeus profundus, elektromyographisch ist aktive und chronische Denervierung im M. extensor digitorum brevis nachweisbar. In Fällen mit partiellem vorderen Tarsaltunnelsyndrom wird entweder nur der motorische Ast zum M. extensor digitorum brevis oder nur der sensible Anteil des N. peronaeus profundus nach der Teilung unter dem Ligamentum cruciatum komprimiert. Zwei Fälle mit vollständigem sowie ein Fall mit partiellem vorderen Tarsaltunnelsyndrom werden vorgestellt; Ätiologie, Symptomatologie, Differentialdiagnose und therapeutische Möglichkeiten werden erörtert.

     

An electrophysiological severity scale in tarsal tunnel syndrome

OBJECTIVE: To propose a neurophysiological classification of tarsal tunnel syndrome. MATERIAL AND METHODS: We retrospectively reviewed the medical records of two electromyography laboratories. Case inclusion criteria were based on clinical parameters. Motor conduction velocity, distal motor latency (DML), sensory conduction velocity (SCV) and sensory action potential (SAP) from big toe (T1) and from fifth toe (T5) to medial malleolus were measured in the medial and plantar nerves. When SCVs of T1 and T5 were normal, we considered the difference in T1 SCV between affected and unaffected side and in T1 SCV of the affected side with sural nerve distal SCV. Feet with TTS were classified in six electrophysiological classes: 0, normal SCV and DML; 1, normal absolute SCV with abnormal comparative tests; 2, slowing of T1 and T5 SCV and normal DML; 3, slowing of SCV and DML; 4, absence of T1 and T5 SAPs and abnormal DML; 5, absence of sensory and motor response. RESULTS: A total of 111 feet belonging to 96 patients (27 men, 69 women; mean age 49.6 years) were diagnosed with TTS. T1 and T5 SCV were abnormal in 82 and 73% of cases, respectively, and comparative tests were abnormal in a further 7% of cases. DML was abnormal in 82 feet (73.9%). Eight feet (7%) were without neurographic abnormalities. The distribution of feet in neurophysiological classes was: stage 0, 7%; stage 1, 9%; stage 2, 10%; stage 3, 39%; stage 4, 32%; stage 5, 3%. Higher clinical scores coincided with higher neurographic classes. CONCLUSION: The progression of neurographic abnormalities in TTS reflects the relation between SCV and DML, and between neurographic values and clinical severity. The scale assigns severity classes in a reliable and non-arbitrary way. This classification can easily be used by electrophysiological laboratories with their own electrophysiological techniques and normal values.     

The dilemma of ulnar nerve entrapment at wrist in carpal tunnel syndrome

Objective

The commonest compression neuropathy in human being is carpal tunnel syndrome (CTS). The association between CTS and ulnar nerve entrapment is debatable. The objective of this study is to determine the presence of any association between CTS and ulnar entrapment neuropathy at the wrist.

Patients and methods

To test the hypothesis we conducted a case-control study. Ninety-nine healthy volunteers and 181 patients with established diagnosis of CTS enrolled to the study. Distal latencies, peak latencies and action potentials for sensory branches and distal latencies and action potentials for motor branches of both median and ulnar nerves were measured in totally 378 hands. We conducted independent t-test comparing age and sex between control and patient groups and analysis of variance to compare dichotomous and continuous variables between control group and patient subgroups.

Results

Based on our cutoffs, we found that 7.5% of CTS patients had distal latency ≥2.8 ms for ulnar sensory branches, 4.6% had distal latency ≥3.4 ms for ulnar nerve motor branches and 15% had peak latency ≥3.3 ms for ulnar sensory branches. There was not any statistically significant correlation between subgroups of CTS patients and control group.

Conclusion

The authors suggest that there may not be any association between CTS and ulnar nerve compression at the wrist. We suggest that different racial groups and multiple techniques in performing nerve conduction studies and dissimilar cutoff values for the diagnosis of entrapment neuropathies are the major causes of ambiguity in the literature. More relevant studies will have crucial importance for detecting ulnar nerve entrapment at the wrist in CTS patients.     

Heat sensitivity of sensory fibers in carpal tunnel syndrome

Elevations in temperature may produce conduction block in demyelinated neurons. A well‐described phenomenon in multiple sclerosis, it has also been reported in some patients with inflammatory demyelinating polyneuropathies. We used carpal tunnel syndrome (CTS) as a model to study the effect of heat on nerves with focal demyelination secondary to chronic compression. Compound motor and sensory responses were measured in 12 CTS patients and 12 normal subjects at 32°C and with heating to 42°C. Changes in relative motor response amplitude and area were similar for both normal subjects and CTS patients. In CTS patients, however, sensory response amplitude and area decreased 34.3% and 48.9%, significantly more than the 25.2% and 39.1% reductions in normal subjects (P = 0.021 and P = 0.018 respectively). We hypothesize that these reductions in response amplitude are secondary to the occurrence of heat‐induced conduction block in demyelinated sensory neurons. © 1999 John Wiley & Sons, Inc. Muscle Nerve 22: 37–42, 1999     

Surface electromyographic recording of volitional activity: a technique to detect partial motor conduction block.

Partial motor conduction block, an electrophysiological hallmark of demyelination, helps to identify acquired demyelinating neuropathies but its electrophysiological detection can be difficult. We report a technique that may be helpful in this regard. Twenty-five patients with partial motor conduction block secondary to acquired demyelinating polyneuropathy (ADP), 7 with amyotrophic lateral sclerosis (ALS), 7 with stroke, and 11 control subjects, were studied. Amplitude of compound muscle action potentials was recorded after distal electrical (E) stimulation and for volitionally (V) induced responses in 82 muscles. Mean +/- SD V/E ratio was 12.3 +/- 6.6 for ADP patients, 58.1 +/- 17 for ALS patients, 11.4 +/- 9 for stroke patients, and 55.4 +/- 12.3 for controls. The V/E ratios for patients with partial motor conduction block and stroke were significantly reduced compared with ALS patients and healthy controls (P < 0.05). Surface electromyographic (EMG) recording for determination of the V/E ratio may be a useful technique for detection of a proximal conduction block if a central lesion or poor effort can be excluded. Further study of this novel technique is necessary.     

Multifocal motor neuropathy with conduction block misdiagnosed as multiple entrapment neuropathies

We describe a 58-year-old male with a few years history of multifocal weakness in the upper limbs with minimal to absent sensory complaints. He was diagnosed as having multiple compressive neuropathies, which required repeated decompressive surgeries. Electrodiagnostic studies prior to diagnosis were limited to a few nerves, evaluating only distal segments. Because of delay in making the diagnosis, his condition progressed, and possibly because of the unnecessary surgeries, he developed atrophy in some muscles, which resulted in significant motor disability. He was later diagnosed as having multifocal motor neuropathy with conduction block and has partially responded to intravenous immunoglobulin therapy. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:813–815, 1998.     

Sensory conduction in the syndrome of Guyon's tunnel

Summary The conduction velocity and potentials of the sensory part of the ulnar nerve were studied in the syndrome of Guyon's tunnel. If the superficial branch of the ulnar nerve was injured by entrapment, the sensory conduction velocity was decreased and changes in the sensory potential occurred. The conduction velocity at the forearm remained normal. This aid to diagnosis is recommended in addition to the measurement of conduction velocities in the motor branches to M. abductor digiti minimi and M. interossei dorsales.

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Zusammenfassung Es wird über die Bestimmung der sensibel orthodromen Ulnarisnervenleitgeschwindigkeiten beim Syndrom der Loge de Guyon berichtet. Als typischer Befund für die Beteiligung des Ramus superficialis nervi ulnaris bei einer distalen Ulnarisläsion wird die pathologische Aufsplitterung und Amplitudenverminderung des distalen sensibel orthodromen Ulnarispotentials beschrieben, während die sensible NLG am Unterarm normal ist. Die Methode wird als Ergänzung zur konventionellen Bestimmung der motorischen Überleitungszeit zum M. interosseus dorsalis I und zum M. abductor digiti quinti beim Verdacht auf ein Syndrom der Loge de Guyon empfohlen.

     

Radiation-induced conduction block: resolution following anticoagulant therapy

Neurophysiologic studies documented proximal conduction blocks in a patient harboring a delayed radiation-induced brachial plexopathy. Since anticoagulants have been reported to be beneficial in radiation-induced neuropathies, the patient was started on acenocumarol. After 3 months of treatment there was significant improvement of clinical deficits, which correlated with resolution of conduction blocks. This observation suggests that ischemic nerve injury leading to disruption of the conduction properties of motor axons contributes to the pathogenesis of delayed radiation-induced peripheral nerve injuries.     

Stimulation distal to the lesion in patients with carpal tunnel syndrome

In patients with carpal tunnel syndrome, low action potential amplitude after stimulation at the wrist (proximal to the lesion) is due to either demyelination or axonal degeneration. Demyelination can be distinguished from axonal degeneration by the presence of amplitude drop across the lesion. Amplitude drop is determined by comparison of action potential amplitude evoked by stimulation at the palm (distal to the lesion) with that of the wrist. Of 59 consecutive CTS patient hands, 36 (61%) showed significant reduction in CMAP and/or antidromic SNAP amplitudes at the wrist compared to the palm, indicating the presence of focal demyelination resulting in conduction block vs. pathologic dispersion with phase cancellation. Moreover, the smaller the wristevoked action potential amplitude, the greater the amplitude drop across the lesion. We conclude that in patients with CTS, as in other entrapment neuropathies, stimulation both proximal and distal to the lesion provides important pathophysiological information about the median nerve lesion. © 1995 John Wiley & Sons, Inc.     

Grading severity of carpal tunnel syndrome in electrodiagnostic reports: Why grading is recommended

Carpal tunnel syndrome (CTS) is not difficult to confirm by electrodiagnosis (EDx), but the challenge lies in whether to grade the severity and the method for doing so. The arguments about grading are discussed, with an emphasis in favor, using a method that relies on the EDx data, but qualifies that it is the median neuropathy being graded and not the syndrome of CTS. Although use of latencies can be arbitrary and misleading, it is possible to apply other criteria, such as low amplitudes or conduction block and denervation, to develop a grading scale that could be applied widely. Several previously published grading schemes are reviewed, and a new method is described that combines the prior ranking criteria into 3 basic categories. Application of a grading system identifies the degree of nerve injury and thus allows the referring physician to utilize optimally the EDx report to manage the patient. Muscle Nerve 48 : 331–333, 2013     

Localization of ulnar neuropathy with conduction block across the elbow

We performed short segment incremental stimulation on 13 consecutive patients with ulnar neuropathy across the elbow (UNE) and conduction block. Conduction block occurred proximal to the medial epicondyle in 62%, at the epicondyle in 23%, and below the elbow in 15%. The ulnar nerve may be more prone to external compression above the elbow than previously recognized. Short segment incremental studies are useful to identify conduction block above the elbow in such patients.     

Central nervous system involvement in multifocal demyelinating neuropathy with persistent conduction block

We report the case of a 27 year-old man treated for bilateral optic neuritis 5 and 3 years before who within a few months developed sensori- motor disorders of the arms and legs Characterized by asymmetric distribution and distal prominence. In addition to sensorimotor defects, which were particularly marked in the left arm and right leg, clinical examination showed nearly generalized areflexia. Electrophysiological studies revealed a rnultifocal neuropathy with persistent distal and proximal conduction blocks associated with a considerable slowing of motor nerve conduction, as well as central nervous system involvement indicated by motor-, somatosensory-, and visual-evoked potentials. CSF analysis showed a mildly elevated protein level; anti-GM, activity was negative. Sural nerve biopsy revealed onion–bulb-like formations, and cerebral MRI showed a small, isolated, and aspecific high signal for white matter. First described by Lewis and Sumner in 1982, rnultifocal neuropathy with persistent conduction blocks may be associated with central demyelination. Our case is compared with 3 similar ones in the literature, and the favorable effects of steroid therapy are emphasized. © 1994 John Wiley & Sons, Inc.     

Carpal tunnel syndrome with normal nerve conduction studies

The utility of electrodiagnostic testing in the evaluation of carpal tunnel syndrome (CTS) has been questioned. We studied patients who met the clinical criteria for CTS and compared patients who had normal nerve conduction studies (NCS) with patients who had abnormal NCS. We found that 25% of the CTS patients without confounding neurologic disorders had normal NCS with median palmar nerve stimulation. Patients with abnormal NCS were older and heavier and had more clinical features of CTS. NCS results could not be predicted accurately from clinical features by use of logistic regression models. This was especially true in clinically borderline cases. NCS did not predict the outcome of conservative management. We concluded that NCS provide independent information in the evaluation of suspected CTS, especially when fewer clinical criteria are present, but that NCS are not helpful in predicting the outcome of nonsurgical management.     

Pressure perception in the normal lower extremity and in the tarsal tunnel syndrome

For quantitative sensory testing to be useful for the management of peripheral nerve problems, a normative database must be developed. The Pressure-Specified Sensory Device™ (PSSD), a handheld instrument whose hemispherical metal probe tips are connected via a force transducer to a computer, has been found reliable and valid for the upper extremity. In the present study, the PSSD was used to measure the cutaneous pressure threshold at four lower extremity sites in 34 normal adults and in 22 patients with tarsal tunnel syndrome (6 bilateral). Each of the 28 limbs that was symptomatic for tarsal tunnel syndrome had a cutaneous pressure threshold greater than the 99% confidence limit of the age-matched controls (≤ 45 years, > 45 years of age). Screening for tarsal tunnel syndrome can be done utilizing the measurement of the two-point static-touch thresholds for pressure and distance. © 1996 John Wiley & Sons, Inc.