Rika Yamauchi

Synovial chondromatosis presenting with cervical radiculopathy: a case report.

Study Design. A case report is presented. Objectives. To report a case of synovial chondromatosis of a cervical facet joint and describe the appearance with magnetic resonance imaging and computed tomography myelography. Summary of Background Data. Synovial chondromatosis is an uncommon disorder characterized by the presence of multiple cartilaginous or osteocartilaginous nodules in the synovium of a joint space. Synovial chondromatosis in the cervical facet joint is rare. Method. A 52-year-old woman experienced the sudden onset of severe pain in the dorsal shoulder girdle and in the ulnar side of her right arm and forearm. This refractory pain only responded to an epidural nerve root block. Neurologic examination showed right nerve root signs that ranged from the C7 to Th1 segments of the spinal cord. Radiologic and electrophysiological examinations were carried out. Result. A mass was found in the right facet joint between C7 and Th1 with magnetic resonance imaging and computed tomography myelography. These investigations clearly indicated the location, size, and extent of the lesion accompanying the irregularity of the joint and osteolytic change. Somatosensory-evoked potentials with right ulnar nerve stimulation indicated a significant conduction block in the lower right cervical nerve roots. After surgical removal of this lesion, the neurologic symptoms markedly improved. The histopathology diagnosed synovial chondromatosis. Conclusion. Synovial chondromatosis should be included in the differential diagnosis of radiculopathies of unknown etiology.

Correlation of bite force with excitation–contraction coupling time of the masseter in myasthenia gravis

OBJECTIVE The aim of this study was to elucidate the relationship between the impairment of excitation-contraction (E-C) coupling of masseter and the bite force in patients with myasthenia gravis (MG). METHODS In 20 patients with MG, masseteric compound muscle action potential (CMAP) and mandibular movement-related potentials (MRP) were recorded simultaneously after stimulating the trigeminal motor nerve with a needle electrode. The E-C coupling time (ECCT) was calculated by the latency difference between CMAP and MRP. Bite force was measured using a pressure-sensitive sheet. Serial assessments of % decrement in masseteric repetitive nerve stimulation (RNS), ECCT, and bite force were performed before and after corticosteroid therapy alone or in various combinations with FK506, cyclosporin A, intravenous immunoglobulin and immunoabsorption. RESULTS Percent amplitude decrement in RNS and ECCT decreased significantly accompanying an increase in bite force after treatment. Simple regression analysis demonstrated a linear correlation among % decrement, ECCT and bite force. However, ECCT shortening accompanying bite force recovery without reduction in % decrement was observed in 4 patients. CONCLUSIONS Masseteric E-C coupling is impaired in some MG patients, and functional recovery of E-C coupling contributes at least in part to the increase in bite force after treatment. SIGNIFICANCE Impaired E-C coupling contributes to muscle weakness in patients with MG.

Contribution of anti-ryanodine receptor antibody to impairment of excitation-contraction coupling in myasthenia gravis.

OBJECTIVE The aim of this study was to elucidate the relationship between the impairment of excitation-contraction (E-C) coupling and anti-ryanodine receptor (RyR) antibody in patients with myasthenia gravis (MG). METHODS Masseteric compound muscle action potential (CMAP) and mandibular movement-related potentials (MRPs) were recorded simultaneously after stimulating the trigeminal motor nerve with a needle electrode. The E-C coupling time (ECCT) was calculated as the latency difference between CMAP and MRP. For each patient, we selected a representative data set when there was no abnormal decrement in response to repetitive nerve stimulation. The 26 data sets were divided into an anti-RyR-positive group (n=12) and an anti-RyR-negative group (n=14). RESULTS Masseteric ECCT was significantly longer (p=0.017) in anti-RyR-positive group (median, mean, range; 3.6, 3.8, 3.0-5.9 ms) than in anti-RyR-negative group (3.1, 3.1, 2.7-4.0) although there were no significant differences in masseteric CMAP amplitude and % decrement between the two groups. The bite force was significantly lower in anti-RyR-positive group than in normal controls. CONCLUSIONS Presence of anti-RyR antibodies is associated with significantly prolonged masseteric ECCT compared to absence of the antibodies in MG. SIGNIFICANCE Anti-RyR antibody contributes to E-C coupling impairment in the masseter muscle in patients with MG.

Early effect of tacrolimus in improving excitation–contraction coupling in myasthenia gravis

OBJECTIVES Tacrolimus (FK506) is a macrolide T-cell immunomodulator used to treat myasthenia gravis (MG). Besides immunosuppression, tacrolimus has been reported to have the potential to increase muscle strength by enhancing ryanodine receptor (RyR) function. However, few attempts have been made to demonstrate the early effect of tacrolimus as an RyR enhancer in clinical investigation. METHODS In 20 MG patients, masseteric compound muscle action potential (CMAP) and mandibular movement-related potentials (MRPs) were recorded simultaneously after stimulating the trigeminal motor nerve with a needle electrode. The excitation-contraction (E-C) coupling time (ECCT) was calculated by the latency difference between CMAP and MRP. Bite force was measured using a pressure-sensitive sheet. Serial assessments of % decrement in masseteric repetitive nerve stimulation (RNS), ECCT and bite force were performed before and within 4 weeks of tacrolimus (3 mg day(-1)) treatment. The median (mean, range) interval of assessment was 2 (2.4, 1-4) weeks. We also measured serum antibodies against RyR, acetylcholine receptor and muscle-specific receptor tyrosine kinase. RESULTS Bite force increased after tacrolimus treatment accompanying clinical improvement assessed by Myasthenia Gravis Foundation of America classification, but the bite force difference did not reach statistical significance. Wilcoxon matched-pairs signed-ranks test detected a significant ECCT shortening in 12 patients assessed after 1-2 weeks of tacrolimus treatment as well as in eight patients assessed after 3-4 weeks. In contrast, masseteric CMAP and % decrement showed no significant changes after short-term tacrolimus treatment. CONCLUSIONS Tacrolimus induces ECCT shortening accompanying clinical improvement despite no improvement in % decrement within 2 weeks. SIGNIFICANCE This early effect of tacrolimus may imply a pharmacological enhancement of RyR function to improve E-C coupling in MG.

[Dramatic seizure reduction with levetiracetam in adult Dravet syndrome: a case report].

A 28 year-old man who had been diagnosed as having Dravet syndrome (DS) since his childhood by a pediatric hospital was referred to our department from the local pediatric clinic. Until then, his seizures were medically intractable, and generalized tonic-clonic convulsions had occurred monthly even when administered enough valproate, zonisamide and clorazepate. After adding levetiracetam (LEV) to his drug regimen at the age of 29, the seizures disappeared for more than one year. LEV was found to be effective in this adult patient as well as in a series of children affected with DS.

Impaired post-tetanic potentiation of muscle twitch in myasthenia gravis

OBJECTIVE The aim of this study was to evaluate post-tetanic potentiation of muscle twitch in myasthenia gravis (MG). METHODS Post-tetanic potentiation was evaluated by recording the compound muscle action potential (CMAP) of abductor pollicis brevis and movement-related potential (MRP) of the thumb using an accelerometer after tetanic stimulation of the median nerve at the wrist. After baseline recording, tetanic stimulation was delivered to the median nerve at a frequency of 10 Hz for 10s. The CMAP and MRP were successively recorded at baseline and at 5, 10, 30, 60, 90 and 120 s after tetanic stimulation. The chronological changes of CMAPs and MRPs were recorded bilaterally in 11 patients with MG, 9 patients with myopathies (disease controls), and 25 healthy control subjects. RESULTS Maximal acceleration of MRP was significantly elevated during 10s after tetanic stimulation without any CMAP changes in all groups. However, statistical analysis detected a significant decrease in post-tetanic potentiation of maximal acceleration of MRP in MG patients only compared to healthy controls, but not in myopathy patients, which may imply impairment of excitation-contraction coupling in MG. CONCLUSIONS Post-tetanic potentiation of muscle twitch is significantly diminished in MG, suggesting impaired excitation-contraction coupling. SIGNIFICANCE Measurement of post-tetanic potentiation using an accelerometer is a simple and sensitive method to detect impairment of excitation-contraction coupling in MG.

O-3-21. Electrophysiological evaluation of peripheral neuropathy in hereditary spinocerebellar ataxia

Peripheral neuropathy often occurs in hereditary spinocerebellar ataxia (hSCA), but the features of nerve involvement have not been fully investigated. We evaluated the prevalence of peripheral neuropathy in hSCAs and classified the underlying pathologies into length-dependent axonopathy and neuronopathy based on sural/radial amplitude ratio (SRAR). SRAR has been reported as a sensitive indicator to differentiate the pathology of peripheral neuropathy. In this study, we defined SRAR less than 0.3 as length-dependent axonopathy, and SRAR more than 0.3 as neuronopathy. We evaluated 22 patients with hSCA (2 patients with SCA1, 1 with SCA2, 12 with SCA3, 2 with SCA6, and 5 with unknown genotypes) and 9 patients with sporadic SCA. Peripheral neuropathy was observed in 13 patients with hSCA (1 SCA1, 1 SCA2, 10 SCA3 and 1 with unknown genotypes). Ten of 13 patients (77%) showed less than SRAR 0.3, which coincided with length-dependent axonopathy. Furthermore, during follow-up for 3 years, three of 5 patients turned into the feature of length-dependent axonopathy from that of neuronopathy. These results indicate that the sural SNAPs might decrease earlier than the radial SNAPs in hSCAs. In conclusion, the length-dependent axonopathy is the dominant form of peripheral neuropathy in patients with hSCA.

Effect of local cooling on excitation-contraction coupling in myasthenic muscle: Another mechanism of ice-pack test in myasthenia gravis

OBJECTIVE The ice-pack test is a convenient diagnostic testing procedure for myasthenia gravis (MG). We investigated the underlying mechanism of the ice-pack test performed on bilateral masseters. METHODS We performed trigeminal repetitive nerve stimulation (RNS), excitation-contraction (E-C) coupling assessment (Imais method) and bite force measurement before and after cooling of the masseters in MG patients and normal controls. After placing the ice-pack on the masseters for 3min, serial recordings of the three tests were performed at various time intervals during 10min after cooling. RESULTS The bite force increased significantly after cooling in ice-pack-positive MG patients. The acceleration and acceleration ratio (acceleration at a given time to baseline acceleration) of jaw movement increased significantly after cooling of the masseters in ice-pack-positive MG patients compared to ice-pack-negative patients and normal controls. The prolonged effect of cooling continued until the end of recording even though decremental response to RNS had returned to baseline value. CONCLUSIONS Cooling of myasthenic muscle may induce two effects. One is relatively short effect on electrical synaptic transmission at the endplate, and another is prolonged effect on E-C coupling in the muscle. SIGNIFICANCE The ice-pack test induces a prolonged effect of ameliorating impaired E-C coupling in MG.