Pathophysiology of unilateral asterixis due to thalamic lesion.

OBJECTIVE: Unilateral asterixis has been reported in patients with thalamic lesion. This study aims at elucidating the pathophysiology of the thalamic asterixis. METHODS: Two cases with unilateral asterixis caused by an infarction in the lateral thalamus were studied by analysing the asterixis-related cortical activities, transcranial magnetic stimulation (TMS) for motor cortex excitability and probabilistic diffusion tractography for the thalamo-cortical connectivity. RESULTS: Averaging of electroencephalogram (EEG) time-locked to the asterixis revealed rhythmic oscillations of a beta band at the central area contralateral to the affected hand. TMS revealed a decrease in the motor evoked potential (MEP) amplitude and a prolongation of the silent period (SP). The anatomical mapping of connections between the thalamus and cortical areas using a diffusion-weighted image (DWI) showed that the lateral thalamus involved by the infarction was connected to the premotor cortex, the primary motor cortex (M1) and the primary somatosensory cortex (S1) of the corresponding hemisphere. CONCLUSIONS: The thalamic asterixis is mediated by the sensorimotor cortex, which is subjected to excessive inhibition as a result of the thalamic lesion involving the ventral lateral nucleus. SIGNIFICANCE: This is the first demonstration of participation of the sensorimotor cortex in the generation of asterixis due to the lateral thalamic lesion.

[A case of Guillain-Barré syndrome accompanied by syndrome of inappropriate secretion of antidiuretic hormone].

A 73-year-old Japanese male was admitted because of difficulty in standing up after acute upper respiratory inflammation with mild fever followed by watery diarrhea. Neurological examination revealed moderate proximal muscle weakness and loss of tendon reflexes in all extremities. The blood sodium level was 106 mEq/l on admission. The blood level of antidiuretic hormone (ADH), renin and aldsterone was 11.3 pg/ml (normal value 0.3-4.2), 0.2 ng/ml/h (0.2-2.7) and less than 10.0 pg/ml (38.9-307.0), respectively. The plasma osmolarity was 221 mOsm/kg (270-295), and the urine osmolarity was 416 mOsm/kg (50-1400). EMG and nerve conduction studies suggested acute demyelination in the motor and sensory nerves. CSF revealed 10 cells/mm3 and elevated protein to 98 mg/dl. The clinical course, laboratory data and electrophysiological findings suggested coexistence of the syndrome of inappropriate secretion of ADH (SIADH) and Guillain-Barré syndrome (GBS) from the very early clinical stage of the diseases. The clinical and laboratory findings improved after intravenous administration of saline over three weeks. When GBS is associated with SIADH, hyponatremia is commonly seen at the peak of motor paralysis, often accompanied by autonomic or respiratory failure requiring mechanical ventilation. This was not the case in the present patient. It is postulated that SIADH, like GBS, might be caused by an autoimmune mechanism.

[A case presenting with both features of essential tremor and Parkinson tremor].

A 78-year-old woman had postural and action tremor in hands since age of late 20's, though without much difficulty in daily living. Since age 76, she has had an increasing difficulty in walking and postural balance, with some worsening of hand shaking as well. She also noted to have head shaking, involuntary movements in the mouth, and some difficulty in swallowing. Reportedly both of her parents and her brother had hand tremor. Neurologically she had resting, postural and action tremors in hands more on the left. She also had marked rigidity in the neck and moderate cogwheel rigidity in all limbs more on the left, moderate bradykinesia, markedly stooped posture with relatively wide base, slow and small-paced gait, and poor postural balance more posteriorly. Thus, it is most likely that the present case suffered from essential tremor and later developed Parkinson disease. Power spectrum analyses of surface electromyogram and accelerometer showed the peaks at 4.3 Hz for the resting tremor, and 3.1 and 5.2 Hz for the postural tremor. Furthermore, significant EEG-EMG coherence was seen at the peaks of 4.3 and 5.2 Hz, suggesting possible involvement of sensori-motor cortex for generation of both tremors. When the postural tremor was loaded with 500 g weight, the peak of power spectrum and EEG-EMG coherence showed the broader pattern with the maximal peak at 4.3 Hz, exactly the same frequency as that of the resting tremor. These findings may be explained by postulating that the 4.3 Hz peak of the resting tremor became apparent by loading because 5.2 Hz peak of the postural tremor was suppressed by the loading. The peak of the postural tremor at 3.1 Hz which was not detected by EEG-EMG coherence suggested that the tremor for 3.1 Hz was not involved to sensori-motor cortex for generation.

[Concurrence of myasthenia gravis, polymyositis, thyroiditis and eosinophilia in a patient with type B1 thymoma].

We presented a 43-year-old Japanese woman who acutely developed weakness of all extremities and difficulty in swallowing and drooping of eyelids, characterized by easy fatigability at the end of December, 2005. On general physical examination, she had moderate goiter. No cervical lymphadenopathy, cardiac murmur, or skin rash was noted. Neurologically, she had blepharoptosis, more on the right, only in the upright position with easy fatigability and marked weakness in the neck flexor, trunk, and all limb muscles much more proximally than distally. She had neither muscular atrophy nor upper motor neuron sign. Laboratory data showed slight leukocytosis with eosinophilia (up to 31%), and serum creatine kinase was markedly increased to over 2,000 IU/l. TSH receptor antibody (11.9%) and anti-acetylcholine receptor antibody (46.6 nmol/L) were also increased. Edrophonium test was positive. Electrophysiologically, muscle evoked potentials by repetitive motor nerve stimulation showed 13% and 50% waning in abductor pollicis brevis and deltoid muscle, respectively, at low frequency and no waxing at high frequency. Needle EMG showed fibrillation potentials and positive sharp waves in proximal muscles. Polymyositis was diagnosed by muscle biopsy which showed infiltration of lymphocytes in the endomysium and around non-necrotic muscle fibers. Upper arm muscle MRI showed multifocal high signal intensity lesions on T2-weighted images which were likely related to myositis. This finding is atypical for polymyositis. X-ray and CT of chest showed a mass lesion in the left pulmonary hilum, which was histologically diagnosed as type B1 thymoma. Thus, the present case had myasthenia gravis, polymyositis, thyroidititis and eosinophilia associated with type B1 thymoma. After the thymectomy, corticosteroid administration and immunoadsorption therapy, clinical symptoms and all laboratory abnormalities markedly improved.