Tibial nerve SEPs in diagnosing lumbar spinal stenosis: The utility of segmental evaluation using P15 and N21.

Objective: To establish the utility of the additional evaluation of the P15 potential generated at the greater sciatic foramen in the tibial nerve somatosensory evoked potentials (SEPs) in diagnosing lumbar spinal stenosis (LSS). Methods: We retrospectively reviewed tibial nerve SEP findings in patients having MRI-confirmed LSS at the cauda equina or conus/epiconus region. P15 and N21 potentials were recorded and the following findings were defined as localizing abnormalities: 1) normal P15 latency either with prolonged P15-N21 interval or with absent N21; 2) decreased ratio of the N21 amplitude to P15 amplitude. As non-localizing abnormalities, N21 and P38 latencies were also evaluated. Tibial nerve F-wave findings were also investigated. Results: According to the entry criteria, 18 patients were included, 15 with cauda equina lesions and 3 with conus/epiconus lesions. Localizing abnormalities in SEPs were found in 67% of patients, achieving significantly higher sensitivity than delayed P38 latency (28%), and higher sensitivity than N21 abnormalities (39%), though this was not significant. Localizing abnormalities were observed even in 6 out of 11 patients lacking both sensory symptoms and signs. Tibial nerve F-wave was abnormal in 36% of 14 patients with F-wave examinations, whereas the localizing abnormalities in SEPs were found in 64% of the same patient population. P15 amplitude was depressed in 4 patients (22%), which may indicate the involvement of the dorsal root ganglion in LSS, although its latency was normal even for these patients. Conclusions: Tibial nerve SEPs with the recording of P15 and N21 potentials achieved sufficiently high sensitivity in diagnosing LSS. They have the advantage over F-wave in that they can localize the lesion at the cauda equina or conus/epiconus level. Significance: Tibial nerve SEPs are promising in evaluating LSS, especially in documenting sensory tract involvement in cases lacking sensory symptoms/signs.

Far-field potential of the compound muscle action potential as a reliable marker in amyotrophic lateral sclerosis.

INTRODUCTION/AIMS: Reliable neurophysiological markers in amyotrophic lateral sclerosis (ALS) are of great interest. The compound muscle action potential (CMAP) amplitude has been a conventional marker, although it is greatly influenced by the electrode position. We propose the far-field potential of the CMAP (FFP-CMAP) as a new neurophysiological marker in ALS. METHODS: Patients with ALS and age-matched healthy controls were enrolled. We used a proximal reference (pref) in addition to the conventional distal reference (dref). Routine CMAP was recorded from the belly-dref lead and FFP-CMAP from the dref-pref lead for the ulnar and tibial nerves. Multiple point stimulation motor unit number estimation (MUNE) was also examined in the ulnar nerve. Inter-rater reproducibility was evaluated by two examiners, and some patients were followed up every 3 mo for 1 y. RESULTS: We tested 17 patients with ALS and 10 controls. The amplitudes of routine CMAP and FFP-CMAP in the ulnar and tibial nerves, and hypothenar MUNE value in the ulnar nerve were significantly decreased in ALS compared to controls. Ulnar FFP-CMAP achieved the highest inter-rater intraclass correlation coefficient (ICC) value (0.942) when compared with routine CMAP (0.880) and MUNE (0.839). The tibial FFP-CMAP had a higher ICC value (0.986) than the routine CMAP (0.697). In this way, the FFP-CMAP showed high inter-rater reproducibility because its shape was not much influenced by the electrode position. During 1-y follow-up, decline of CMAP, FFP, and MUNE showed significant correlations with the Amyotrophic Lateral Sclerosis Functional Rating Scale - Revised (ALSFRS-R). DISCUSSION: The FFP-CMAP shows promise as a reliable marker for ALS.

Utility of the tibial nerve somatosensory evoked potentials in differentiating between neuromyelitis optica spectrum disorders and multiple sclerosis.

BACKGROUND: Somatosensory evoked potentials (SEPs) are widely used for the diagnosis and evaluation of neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS). However, whether the parameters of tibial nerve SEPs can help to distinguish NMOSD from MS remains unclear. Thus, the aim of this study was to investigate the utility of tibial nerve SEP parameters in differentiating patients with NMOSD and MS. METHODS: The clinical data of patients with NMOSD or MS treated in our institution between 2005 and 2021 were retrospectively extracted from our electronic database. Additional inclusion criteria were presentation with sensory symptoms in the lower extremities with corresponding lesions in the magnetic resonance images as well as available data on anti-aquaporin-4 antibodies and tibial nerve SEPs. The Z-scores of the N21-P38 interval (central sensory conduction time), P38 latency, and P38 amplitude were compared between the patients with NMOSD and MS. The relationship of disease severity with the parameters of the tibial nerve SEPs was also evaluated. RESULTS: Twenty patients with NMOSD and 13 patients with MS were enrolled. The Z-scores of the N21-P38 interval and P38 latency were significantly higher in the MS group than in the NMOSD group (p < 0.05 and p < 0.01, respectively), whereas there was no difference in the Z-scores of the P38 amplitude between the two groups. In the MS group, only the N21-P38 interval and P38 latency were significantly correlated with disease severity (p < 0.05 and p < 0.01, respectively). In contrast, none of the tibial nerve SEP parameters were significantly correlated with disease severity in the NMOSD group. CONCLUSION: Evaluation of the N21-P38 interval and P38 latency in tibial nerve SEPs potentially helps in differentiating between NMOSD and MS.

The influence of right-left error in the placement of the Cc electrode in tibial nerve somatosensory evoked potentials (SEPs).

OBJECTIVE: At our laboratory, we routinely record tibial nerve somatosensory evoked potentials (SEPs) using 5 channels including the second cervical vertebra (C2S)-contralateral central area (Cc) and Cz' (2 cm posterior to Cz)-Cc derivations. In a man with lumbar spondylotic myelopathy, symptoms improved after surgery, although the N21-P38 interval was markedly prolonged in comparison with that before surgery. We presumed that the Cc electrode was actually placed on the ipsilateral central area (Ci) at the second examination. Inspired by this episode, we investigated the influence of the right-left error in the placement of the Cc electrode. METHODS: Subjects were 20 healthy volunteers. Tibial nerve SEPs were recorded with 8 leads including Cz'-Cc, Cz'-Ci, C2S-Cc and C2S-Ci. RESULTS: For the Cz'-Ci lead, the P38 potential diminished in amplitude, was absent or became negative. For the C2S-Ci lead, a large negative potential corresponding to the phase reversal of P38 was frequently observed. CONCLUSIONS: Tibial nerve SEPs using the Cz'-Cc or C2S-Cc lead are distorted if the Cc electrode is placed on the opposite side. SIGNIFICANCE: When a strange result is obtained in tibial nerve SEPs, we should check for a right-left error in the Cc electrode placement.

A new method to define cutoff values in nerve conduction studies for carpal tunnel syndrome considering the presence of false-positive cases.

BACKGROUND: Nerve conduction studies (NCS) are useful tools for diagnosing carpal tunnel syndrome (CTS). Establishing the normal values is the first step required for utilizing NCS for diagnosis. Previous epidemiological studies demonstrated the presence of fairly large number of false-positive subjects regarding NCS among control population, which has not been properly considered in past studies. This study proposed a new method to address this issue. METHODS: Non-diabetic 144 CTS patients were retrospectively enrolled using clinically defined inclusion criteria. Controls consisted of 73 age-matched volunteers without hand symptoms. Six NCS parameters were evaluated including peak-latency difference by the thumb method (thumbdif) and that by the ring-finger method (ringdif). The Youden index of the receiver operator characteristic curve was used both to judge the sensitivity of a parameter and to identify false-positive cases that were thought to have subclinical median neuropathy at the wrist. The linear function of six parameters was constructed, and the coefficient for each parameter was variously changed. RESULTS: When the Youden index took on the maximum value, seven control subjects (10%) were identified as false-positive and were excluded from the calculation of normal values. The most sensitive parameter before exclusion was thumbdif, whereas ringdif became the most sensitive after exclusion. The cut-off value for ringdif was 1.15 ms before exclusion, but was 0.37 ms after exclusion. CONCLUSION: This method can be widely applied to solve the statistical problem when the gold standard is lacking, and the outside reference standard is not completely reliable.

Novel SLC20A2 variant in a Japanese patient with idiopathic basal ganglia calcification-1 (IBGC1) associated with dopa-responsive parkinsonism.

Idiopathic basal ganglia calcification-1 (IBGC1) is an autosomal dominant disorder characterized by calcification in the basal ganglia, which can manifest a range of neuropsychiatric symptoms, including parkinsonism. We herein describe a 64-year-old Japanese IBGC1 patient with bilateral basal ganglia calcification carrying a novel SLC20A2 variant (p.Val322Glufs*92). The patient also presented with dopa-responsive parkinsonism with decreased dopamine transporter (DAT) density in the bilateral striatum and decreased cardiac 123I-meta-iodobenzylguanidine uptake.

Pembrolizumab-induced Ocular Myasthenia Gravis with Anti-titin Antibody and Necrotizing Myopathy.

A 73-year-old man developed diplopia after the administration of pembrolizumab for lung adenocarcinoma. He had ptosis and external ophthalmoplegia without general muscle weakness. Serum CK levels were elevated. Although autoantibodies to acetylcholine receptor and muscle-specific kinase, the edrophonium test, and the repetitive nerve stimulation test were all negative, anti-titin autoantibody was positive, leading to the diagnosis of myasthenia gravis (MG). Muscle pathology showed necrotizing myopathy with tubular aggregates. Unlike previously reported cases of pembrolizumab-associated MG, the present case showed ocular MG. This is the first case of pembrolizumab-associated MG with anti-titin antibody, as well as the first case with tubular aggregates.

C8 and T1 innervation of forearm muscles.

OBJECTIVE: C8-dominant innervation of ulnar-innervated and T1-dominant innervation of median-innervated intrinsic hand muscles have been suggested, although less is known regarding forearm muscles. We aimed to determine myotomal innervation of the forearm muscles based on the clinical and electromyographial findings of patients with C8 or T1 lesions. METHODS: Medical Research Council scale and EMG findings were retrospectively reviewed in 16 patients with C8 lesions (2 postmedian sternotomy C8 plexopathy and 14 C8 radiculopathy) and 9 patients with T1-dominant lesions (8 true neurogenic thoracic outlet syndrome and 1 T1 radiculopathy). RESULTS: Clinical and EMG findings revealed T1-dominant innervation of the flexor digitorum superficialis, flexor digitorum profundus of the index finger, abductor pollicis brevis, and flexor pollicis longus muscles, and C8-dominant innervation of the flexor carpi ulnaris, flexor digitorum profundus of the little finger, and digit extensors innervated by the posterior interosseous nerve. The first dorsal interosseous, and abductor digiti minimi muscles seem to be innervated by both C8 and T1 roots. CONCLUSIONS: C8-dominant innervation of ulnar-innervated muscles and T1-dominant innervation of median-innervated muscles are also evident for forearm flexor muscles. SIGNIFICANCE: Such an additional evidence for myotomal innervation will improve localization in clinical as well as electrophysiological diagnoses.

Duration of the distal compound muscle action potential for diagnosis of chronic inflammatory demyelinating polyneuropathy: effects of low-cut filters.

PURPOSE: In current electrodiagnostic criteria for chronic inflammatory demyelinating polyneuropathy, the cutoff values of distal compound muscle action potential (DCMAP) duration are defined using electromyogram low-cut filter setting of 20 Hz. We aimed to assess effects of low-cut filter on DCMAP duration (10 vs. 20 Hz). METHODS: We prospectively measured DCMAP duration in 130 normal controls and 42 patients, fulfilling diagnostic criteria for typical chronic inflammatory demyelinating polyneuropathy by European Federation of Neurological Societies/Peripheral Nerve Society. RESULTS: Distal compound muscle action potential duration was significantly shortened with 20-Hz than 10-Hz filtering. When the cutoff values were defined as the upper limit of normal (ULN, mean + 2.5SD), the sensitivity/specificity was 67%/95% in 10-Hz recordings, and 69%/95% in 20-Hz recordings. This diagnostic accuracy was similar to that defined by receiver operating characteristic analyses. CONCLUSIONS: Distal compound muscle action potential duration significantly affected by the low-cut electromyogram filter setting, but with at least 10 and 20 Hz, the diagnostic accuracy is similar.

A new pitfall in a sensory conduction study of the lateral antebrachial cutaneous nerve: spread to the radial nerve.

INTRODUCTION: We describe a previously unreported pitfall, spread of the stimulus at the elbow to the radial nerve, in an antidromic sensory nerve conduction study of the lateral antebrachial cutaneous (LAC) nerve. METHODS: Subjects consisted of 80 healthy volunteers, and both sides were examined for each subject. Besides routine recording of the LAC nerve, sensory nerve action potentials (SNAPs) of the radial nerve were recorded distally. RESULTS: The spread phenomenon occurred in 73 of 160 arms (46%), and the SNAP amplitude increased due to contamination of the radial SNAP up to 6.7 times the genuine LAC SNAP. In 10 arms (6%), the spread started before the LAC SNAP was saturated, and the genuine LAC SNAP was unknown due to an anatomical variation in at least 1 arm. CONCLUSIONS: Without monitoring distal radial SNAPs, the spread phenomenon will remain unrecognized. This pitfall undermines the reliability of the test.

Guillain-Barré syndrome in two patients with respiratory failure and a review of the Japanese literature.

We described two patients with Guillain-Barré syndrome and respiratory failure with or without mechanical ventilation. Case 1 was a 44-year-old man who treated as pneumonia under mechanical ventilation for a month and transferred to our hospital with unsuccessful weaning trials because of phrenic nerve palsy. Case 2 was a 74-year-old man who presented with aspiration pneumonia because of bulbar palsy. The present two cases with review of the Japanese literature showed that antecedent infection with initial symptoms within the most recent 5 to 46 days is a clinical clue to the diagnosis even in patients with Guillain-Barré syndrome accompanied by respiratory failure.

Decremental responses to repetitive nerve stimulation (RNS) in motor neuron disease.

OBJECTIVE: To clarify the features of decremental responses following repetitive nerve stimulation in patients with motor neuron diseases (MNDs), in comparison with myasthenia gravis (MG). METHODS: The subjects consisted of 48 MND, 39 generalized MG and 19 ocular MG patients. Six muscles, both proximal and distal muscles, were tested. RESULTS: Significant decrements (>5%) in at least one muscle were observed in 83% of the MND patients, and 74% and 47% of the generalized MG and ocular MG patients, respectively. Decrements were more frequently observed in the proximal muscles both in MND and MG patients (deltoid 76% and 62%, and trapezius 71% and 51% for MND and generalized MG, respectively), suggesting lower safety factors in neuromuscular transmission in those muscles. Decrements in the nasalis were rare in MND (8%) in comparison with generalized MG (54%). CONCLUSIONS: Decremental responses were frequently observed in MND patients. There were small differences between MND and MG regarding the distribution and other features of decrements, such as the degree of the U-shape or the responses to different stimulus frequencies and to brief exercise. SIGNIFICANCE: These results imply that the underlying mechanism regulating the decrements is common to MND and MG.

[Brainstem variant of reversible posterior leukoencephalopathy syndrome with a prolonged clinical course: a case report].

A 38-year-old man gradually developed gait instability, dysarthria, and dysphagia over two months associated with an elevated blood pressure after starting hemodialysis therapy for diabetic nephropathy. Brain MRI studies indicated vasogenic edema in the brainstem, extending from the lower midbrain to the upper medulla oblongata. The patient's high blood pressure was refractory to treatment, and his neurological disabilities and MRI abnormalities progressed. FDG-PET, MR spectroscopy, and cerebrospinal fluid studies did not suggest neoplastic pathologies. The patient was diagnosed with a brainstem variant of reversible posterior leukoencephalopathy syndrome, and received three courses of steroid pulse therapy. After the pulse therapy, the clinical manifestations and MR findings improved. By maintaining strict management of blood pressure and body water balance during hemodialysis, he did not experience any further clinical exacerbation, and the lesion on MR images continued to regress. Ten months after the pulse therapy, T1-weighted images showed slightly hyperintense signal. This case suggests that reversible posterior leukoencephalopathy syndrome (RPLS) may take a chronic clinical course without acute onset.

[A case of multiple brain abscess effectively markedly responded to high dose panipenem/betamipron administration].

A 54-year-old, previously healthy female experienced headache, nausea and vomiting, and consulted our hospital regarding her symptoms. Her cerebrospinal fluid (CSF) showed leukocytosis with polymorphonucleosis and hypoglycemia, thus she was diagnosed with bacterial. She admitted to our hospital and combination therapy of ampicillin and cefotaxime was started. CSF and blood cultures was negative. On the third hospital day, despite a decrease in her CSF cell count, her consciousness level decreased and neck stiffness worsened. On the seventh hospital day, the CSF cell count increased again, and we changed antibiotics to panipenem/betamipron (PAPM/BP) at 4 g/day. On the tenth hospital day, the CSF cell count decreased, but by the twelfth hospital day her consciousness had deteriorated to a drowsy state. Brain CT and MRI revealed multiple brain abscesses and hydrocephalus. We increased the dose of PAPM/BP up to 8 g/day, and her neurological, CSF and brain MRI findings subsequently improved. The patient was discharged from our hospital on the sixty-ninth hospital day. As the frequency of beta-lactamase-producing bacteria is currently increasing, carbapenems should be considered as first choice of antibiotics for the initial treatment of multiple brain abscess.

[Steroid therapy for multiple sclerosis].

The cause of multiple sclerosis(MS) is still obscure. However, recent therapy is making a dramatic progress. The steroid is traditional therapy, especially the common use of methylprednisolone in management of attacks of MS is based on high-dose intravenous methylprednisolone. This section are described steroid therapy of history(ACTH therapy, High-dose intravenous methylprednisolone therapy, ACTH therapy vs high-dose intravenous methylprednisolone therapy, and long term effects of steroid therapy), high-dose oral and intravenous methylprednisolone therapy, oral therapy after steroid pulse therapy and long term effects of steroid.