Surgical treatment of sural nerve entrapment aided by imaging- and electrography-based diagnosis: illustrative case.

BACKGROUND: The sural nerve (SN) is a cutaneous sensory nerve that innervates the posterolateral side of the distal third of the leg and lateral side of the foot. The SN has wide variation in its course and is fixed to the subcutaneous tissue and superficial fascia. Idiopathic spontaneous SN neuropathy is rarely surgically treated because of the difficulty in detecting SN entrapment. OBSERVATIONS: Herein, the authors present a rare case of surgically treated spontaneous SN neuropathy. A 67-year-old male patient presented with right foot pain for several years. Magnetic resonance imaging and ultrasonography showed SN entrapment slightly proximal and posterior to the lateral malleolus. A nerve conduction study showed SN disturbance. After undergoing neurolysis, the patient's foot pain was alleviated. LESSONS: Idiopathic SN neuropathy can be treated surgically when SN entrapment is detected with comprehensive evaluation methods.

Correlation of Baba's diabetic neuropathy classification with various diabetes-related complications.

It is known that Baba's diabetic neuropathy classification (BDC) is useful in quantitative evaluation of Diabetic polyneuropathy (DPN). In this study, we aimed to investigate the possible association between BDC and various diabetic microvascular and macrovascular complications in patients whose neuropathy was evaluated with BDC. As the results, BDC was significantly correlated with the severity of diabetic retinopathy and nephropathy. BDC was also significantly correlated with history of myocardial infarction or cerebral infarction, carotid IMT, and ABI. These data suggest that BDC may be useful in predicting the presence of various diabetic microvascular and macrovascular complications. The data also support the idea that we should perform further investigation of other diabetes-related complications in patients with severe DPN.

A novel method to measure sensory nerve conduction of the posterior antebrachial cutaneous nerve.

INTRODUCTION/AIMS: Posterior antebrachial cutaneous (PABC) nerve conduction studies could be useful for distinguishing PABC neuropathy from C7 radiculopathy. In the conventional method using an antidromic method, the sensory nerve action potential (SNAP) is sometimes followed by a large volume-conducted motor potential. In this report we describe a reliable nerve conduction study using an orthodromic method for recording SNAPs of the PABC nerve. METHODS: Thirty-six healthy volunteers participated in this study. PABC SNAPs were recorded by placing a surface-active electrode 2 cm anterior to the lateral epicondyle. The PABC nerve was stimulated 10 cm distal to the active recording electrode along a line from the recording point to the mid-dorsum of the wrist, midway between the radial and ulnar styloid processes. We also performed PABC nerve conduction studies using an antidromic method and compared the findings. RESULTS: PABC SNAPs were recorded bilaterally from all subjects. The mean peak-to-peak amplitude for SNAPs was 13.4 ± 4.8 µV. Mean maximum conduction velocity was 62.7 ± 3.9 m/s and mean negative peak conduction velocity was 51.2 ± 2.6 m/s. The mean side-to-side difference in amplitude was 22.1 ± 16.0%. The mean amplitude of SNAPs obtained by our method was 48.9% higher than that of SNAPs obtained by the conventional method (13.4 vs 9.0 µV; P < .001). In contrast to the conventional method, our method enabled SNAPs to be recorded without a volume-conducted motor potential. DISCUSSION: The higher mean amplitude of SNAPs with our method enables them to be obtained easily.

Anatomical variations of the superficial branch of the radial nerve and the dorsal branch of the ulnar nerve: A detailed electrophysiological study.

INTRODUCTION: In this study we evaluated anatomic variations of the superficial branch of the radial nerve (SBRN) and the dorsal branch of the ulnar nerve (DBUN) electrophysiologically. METHODS: Antidromic nerve conduction studies (NCS) of the SBRN and DBUN were performed on healthy individuals. To identify individual responses from the distal branches of the SBRN and DBUN, sensory nerve action potentials of each finger (lateral side/medial side) were recorded. RESULTS: NCS were performed in 50 hands of 27 healthy control subjects. The thumb and the index finger were supplied by the SBRN in all cases. The lateral and medial sides of the third finger were supplied by the SBRN in 94.0% and 74.0% of the cases, but the lateral and medial sides of the fourth finger were supplied by the SBRN in only 10.0% and 2.0% of cases. The fifth finger and the medial side of the fourth finger were always supplied by the DBUN. The lateral side of the fourth finger was supplied by the DBUN in 98.0% of cases, but the lateral and medial sides of the third finger were supplied by the DBUN in 40.0% and 70.0% of cases. Dual innervation by the SBRN and DBUN was found in 34.0% and 46.0% of the lateral and medial sides of the third finger, but in only 8.0% and 2.0% of the lateral and medial sides of the fourth finger. DISCUSSION: There are considerable anatomic variations of the SBRN and DBUN in healthy individuals.

Relationship between the Diabetic Polyneuropathy Index and the Neurological Findings of Diabetic Polyneuropathy.

Objective To achieve an accurate quantification in diabetic polyneuropathy (DPN), we developed a new electrophysiological index that we called the DPN index. The relationship between the DPN index and the neurological findings in diabetic patients was assessed. Methods The DPN index was calculated by the mean value of percentages of four parameters (tibial compound muscle action potential amplitude / F wave minimum latency, sural sensory nerve action potential amplitude / sensory nerve conduction velocity) against the mean normal values. Twenty healthy subjects were recruited as a control group. Patients A total of 348 diabetic patients who were hospitalized in our hospital during the period from December 2016 to August 2019 were retrospectively studied. The correlations between the DPN index and five neurological findings (subjective sensory symptoms, diminished or absent Achilles tendon reflex, impaired tactile and vibration sense, low coefficient of variation of R-R interval) were evaluated. Results The DPN index in healthy subjects was 129.3±32.7%. The DPN index in diabetic patients with one or more neurological findings was significantly lower than that in diabetic patients without any neurological findings (p<0.01: 89.3±27.8% vs. 118.4±21.2%). For each of the five neurological findings, the DPN index in the group with an abnormality was significantly lower than that in the group without any abnormality (each p<0.01). Spearman's correlation coefficients indicated that a greater number of neurological findings resulted in a lower DPN index (r=-0.711, p<0.01). Conclusion Our study suggested that the DPN index is useful for evaluating the severity of DPN.

Influence of placement sites of the active recording electrode on CMAP configuration in the trapezius muscle.

OBJECTIVE: We investigated how the active electrode placement site influences compound muscle action potential (CMAP) configuration of the upper trapezius muscle (TM). METHODS: A nerve conduction study of the accessory nerve was performed, and the CMAPs obtained with two different placement sites, i.e., placement of the active recording electrode on the belly of the upper TM (CMAP-A) and placement of the electrode 2 cm behind the belly (CMAP-B), were compared. CMAPs were also obtained with the active recording electrode placed in the supraspinous fossa (CMAP-C). RESULTS: All CMAPs were recorded from 21 healthy volunteers. The mean peak-to-peak amplitude of CMAP-B was 3.4 mV higher than that of CMAP-A (11.0 ±â€¯4.0 mV vs. 14.4 ±â€¯4.9 mV; P < 0.01). The mean peak-to-peak amplitude of CMAP-C was 10.3 ±â€¯5.0 mV. CONCLUSIONS: CMAP of the upper TM was always higher when the active recording electrode was placed 2 cm behind the belly of the muscle. SIGNIFICANCE: When stimulating the accessory nerve, a current spread occurs to the C5 spinal nerve root and another CMAP originating from the supraspinatus muscle occurs in the supraspinous fossa. The volume conduction from the supraspinatus muscle affects the active recording electrode on the TM, resulting in an increase in CMAP amplitude.

Clinical and pathological findings in familial amyloid polyneuropathy caused by a transthyretin E61K mutation.

Familial amyloid polyneuropathy (FAP) is an autosomal dominant hereditary systemic amyloidosis caused by mutation of the transthyretin (TTR) gene, and usually shows sensory-dominant polyneuropathy and autonomic neuropathy at the initial stage. The pathogenesis of this neuropathy remains unknown, although several mechanisms, including mechanical compression, vessel occlusion, TTR toxicity and Schwann cell dysfunction have been proposed. We describe a patient with late-onset FAP caused by a TTR E61K mutation. Amyloid deposits were not detected in the endoneurium or perineurium of the sural nerve 7years after the onset of the disease, but a marked loss of nerve fibers was observed in the sural nerve. TTR-derived amyloid deposits were confirmed in the peroneus brevis muscle, salivary gland and heart tissue. DNA analysis revealed a heterozygous mutation in TTR. These findings suggest that proximal parts of the peripheral nervous system might be strongly affected by TTR aggregates or amyloid fibrils, and that the blood-nerve barrier in distal parts of peripheral nerves are initially preserved in this patient. This case indicates that several biopsy sites other than nerves may be helpful and necessary for the diagnosis of TTR amyloidosis in mild or late-onset FAP.

A new technique for dorsal sural nerve conduction study with surface strip electrodes.

OBJECTIVE: To obtain higher amplitude of dorsal sural sensory nerve action potentials (SNAPs), we used a new method for dorsal sural nerve conduction study with surface strip electrodes (SSEs). METHODS: Dorsal sural SNAPs were recorded orthodromically. The recording electrodes were placed behind the lateral malleolus. SSEs were attached to the laterodorsal aspect of the foot for stimulation of the dorsal sural nerve (DSN). We also used a conventional method with a standard bipolar stimulator and compared the findings. RESULTS: Dorsal sural SNAPs were recordable bilaterally from 49 healthy volunteers. Mean peak-to-peak amplitude for SNAPs was 12.9±6.3µV, and mean nerve conduction velocity was 44.8±5.5m/s. The mean amplitude of SNAPs obtained by our method was 118.6% higher than that of SNAPs obtained by the conventional method (12.9µVvs. 5.9µV; P<0.001). CONCLUSIONS: The highest amplitude of dorsal sural SNAPs was constantly obtained by SSEs since SNAPs arising from whole digital branches of the DSN could be elicited by placement of SSEs. SIGNIFICANCE: When the DSN supplies more cutaneous branches to the lateral half of the foot, SSEs gives higher amplitude of dorsal sural SNAPs than that of the standard innervation type.

Variations in the distal branches of the superficial fibular sensory nerve.

INTRODUCTION: We evaluated anatomic variations of distal branches of the superficial fibular sensory nerve electrophysiologically. METHODS: Orthodromic nerve conduction studies (NCS) of the first and third branches (M-I, M-III) of the medial dorsal cutaneous nerve and the fourth and fifth branches (I-IV, I-V) of the intermediate dorsal cutaneous nerve (IDCN) were performed. To find anomalous innervations from the dorsal sural nerve (DSN) in the IDCN territory, NCS of the fourth and fifth branches (S-IV, S-V) of the DSN were also performed. RESULTS: All sensory nerve action potentials (SNAPs) of M-I and M-III could be obtained bilaterally from 31 healthy Japanese volunteers. SNAPs of I-IV and I-V were recordable in 85.5% and 43.5% of feet, respectively. Anomalous innervations from the DSN were confirmed in 71.0% of S-IV and 93.5% of S-V. CONCLUSION: These results suggest that anatomical variations in the IDCN territory are very frequent in Japanese subjects. Muscle Nerve 55: 74-76, 2017.

Diagnostic markers of axonal degeneration and demyelination in sensory nerve conduction.

INTRODUCTION: The aim of this study was to formulate diagnostic hallmarks of axonal degeneration and demyelination in sensory nerve conduction studies (NCS). METHODS: We compared nerve conduction data obtained with surface electrode (SE) NCS and on-nerve needle (ONN) NCS in 50 cases of demyelination and 22 cases of axonal degeneration as assessed by sural nerve biopsy. RESULTS: The overall diagnostic sensitivities of sensory nerve conduction were 26% by SE-NCS and 69% by ONN-NCS. The most helpful marker for demyelination was negative-peak nerve conduction velocity (NP-NCV), using a 36% decrease from the means in both techniques. Dispersion was also helpful in identifying demyelination. Low amplitude and absence of compound nerve action potential were indicative of general pathology in SE-NCS but of axonal degeneration in ONN-NCS. CONCLUSION: Although diagnostic sensitivity is low, NP-NCV and dispersion can be used for diagnosis of demyelination in sensory NCS. Muscle Nerve 53: 866-871, 2016.

Whole plantar nerve conduction study with disposable strip electrodes.

INTRODUCTION: A new method to evaluate whole plantar nerve conduction with disposable strip electrodes (DSEs) is described. METHODS: Whole plantar compound nerve action potentials (CNAPs) were recorded at the ankle. DSEs were attached to the sole for simultaneous stimulation of medial and lateral plantar nerves. We also conducted medial plantar nerve conduction studies using an established method and compared the findings. RESULTS: Whole plantar CNAPs were recorded bilaterally from 32 healthy volunteers. Mean baseline to peak amplitude for CNAPs was 26.9 ± 11.8 µV, and mean maximum conduction velocity was 65.8 ± 8.3 m/s. The mean amplitude of CNAPs obtained by our method was 58.2% higher than that of CNAPs obtained by the Saeed method (26.9 µV vs. 17.0 µV; P < 0.0001). CONCLUSIONS: The higher mean amplitude of whole plantar CNAPs obtained by our method suggests that it enables CNAPs to be obtained easily, even in elderly people.

On-nerve needle nerve conduction study in the sural nerve: A new technique for evaluation of peripheral neuropathy.

OBJECTIVE: The objective of this study was to compare the nerve conduction study (NCS) data by the surface electrode (SE)-NCS versus the on-nerve needle (ONN)-NCS and to assess their clinical usefulness in the diagnosis of peripheral neuropathy. METHODS: Sensory compound nerve action potentials (CNAPs) were obtained by the ONN-NCS with needle electrodes placed on the exposed sural nerve during biopsy in 94 patients with peripheral neuropathy. RESULTS: The ONN-NCS is possible in 95% of cases. The ONN-NCS was able to record sensory CNAP in 15% of cases when it was unobtainable in the SE-NCS. The ONN-NCS showed higher amplitude and longer duration of the CNAP but a slower maximum nerve conduction velocity (NCV) than the SE-NCS. The ONN-NCS showed a significantly better concordance with the nerve biopsy findings, especially in demyelinating neuropathy. CONCLUSION: The ONN-NCS is a better electrophysiological test for the histopathological correlation with nerve biopsy. SIGNIFICANCE: The ONN-NCS was able to record sensory CNAP in 15% of cases when it was unobtainable in the SE-NCS.

A novel method to measure sensory nerve conduction of the supraclavicular nerve.

INTRODUCTION: In this report we describe a reliable method for recording sensory nerve action potentials (SNAPs) of the supraclavicular nerve. METHODS: Supraclavicular SNAPs were recorded by placing a surface active electrode at the posterior border of the sternocleidomastoid muscle at a distance of 6 cm from the sternoclavicular joint. The nerve was stimulated at the lower border of the clavicle 4.5 cm lateral to the sternoclavicular joint. RESULTS: Supraclavicular SNAPs were recorded bilaterally from 20 healthy volunteers. Mean onset latency was 1.0 ± 0.2 ms, and mean peak latency was 1.4 ± 0.3 ms. Mean baseline-to-peak amplitude for the SNAPs was 6.1 ± 2.2 µV, and mean maximum conduction velocity was 59.8 ± 6.2 m/s. The mean percentage of side-to-side difference in amplitude was 12.9 ± 11.0%. CONCLUSIONS: Supraclavicular SNAPs could be obtained in all normal subjects. Assessment of supraclavicular nerve conduction is very useful in the diagnosis of supraclavicular neuropathy.

Unilateral calf hypertrophy and focal myositis induced by S1 radiculopathy: dramatic response to steroid treatment.

Unilateral enlargement of the calf in a 57-year-old man with S1 radiculopathy is described in this case report. Short tau inversion recovery-weighted imaging provided evidence of selective hypertrophy and a high signal intensity of the gastrocnemius and soleus. Histopathological analysis of the gastrocnemius revealed an endomysial inflammatory infiltrate and marked denervation lesions. Marked signs of denervation are suggestive of focal myositis secondary to neurogenic damage. The patient was treated with an oral corticosteroid (30 mg/day) and the calf hypertrophy was dramatically reduced within 5 weeks. Our case indicates that steroid therapy should be tried because it may be a potentially treatable disease.

Different characteristic phenotypes according to antibody in myasthenia gravis.

OBJECTIVES: To find the characteristic phenotypes of 3 different types of myasthenia gravis (MG). METHODS: The clinical and electrophysiological features among 15 cases of muscle-specific kinase antibody positive (MuSK Ab+) MG, 59 cases of double seronegative (DSN) MG, and 161 cases of acetylcholine receptor antibody (AChR Ab)+ MG in the University of Alabama at Birmingham were compared. RESULTS: AChR Ab was positive in 69% of cases and MuSK Ab in 6% of cases. MuSK Ab+ MG was more common (14%) in African Americans compared with whites (4%). AChR Ab+ MG is characterized by male predominance, later onset, a fewer cases of ocular MG, and a higher association with thymoma. DSN-MG is characterized by a greater prevalence of ocular MG, milder forms of MG with less number of crisis, and fewer abnormalities in the repetitive nerve stimulation test. MuSK Ab+ MG is characterized by younger age at onset, severe and bulbar forms of MG, predominant faciobulbar neck weakness, and a poor response to edrophonium, anticholinesterase, and intravenous immunoglobulin. Long-term outcome showed no difference among 3 types of MG. CONCLUSIONS: AChR Ab+ MG and DSN-MG are similar, with the exception of less severity in the latter. MuSK Ab+ MG has distinct clinical and electrophysiological features.

[Acute fulminant brachial plexopathy with good recovery: electrophysiological features].

We report a case of fulminant brachial plexopathy with radicular involvement. A 25-year-old man developed acute total monoplegia in the left upper limb. Needle electromyography showed extensive acute denervation in the C5-T1 spinal segments, and peripheral sensory nerve conduction was normal, mimicking a pre-ganglionic lesion. However, left median somatosensory evoked potentials revealed abnormal Erb's point potential, suggesting a brachial plexus lesion. Corticosteroid treatment resulted in good recovery. These findings suggest that the primary pathophysiology was conduction block and this can explain the good clinical recovery in this patient.

Dramatic response of dropped head sign to treatment with steroid in Parkinson's disease: report of three cases.

Neck dystonia is the most common cause of dropped head sign in parkinsonism. Isolated neck extensor myopathy, which is a rare condition, can also cause dropped head sign in parkinsonism, but no improvement has been achieved with immunosuppressive therapy. We report three cases of treatable neck extensor myopathy causing dropped head sign in patients with Parkinson's disease. Needle electromyography and magnetic resonance imaging suggested a restrictive active myopathy affecting neck extensor muscles. All cases responded dramatically to steroid therapy. Routine needle electromyography should be performed to explore treatable myopathy in Parkinson's disease.

Intraoperative on-nerve nerve conduction study and conversion factor in the sural nerve.

To determine the conversion factor (CF) of the sural nerve the correlation between the maximum nerve conduction velocity (NCV) and the diameter of the largest fibers was studied in 30 patients suspected of having neuropathy. Sensory nerve action potentials were obtained by on-nerve needle nerve conduction study using needle electrodes placed on the exposed sural nerve during biopsy. The CF was 4.3 (n = 2) in normal sural nerves and close to the normal value (3.85, n = 4) in axonal neuropathy. The CF in demyelinating neuropathy was smaller than the normal value (2.77, n = 24), indicating disproportionately slower conduction than expected from the diameter of nerve fibers. The CF was helpful in differentiating between demyelinating and axonal neuropathies. We propose that a 36% decrease from the mean value of NCV is a reasonable criterion for demyelination of the nerve.