Relative fatigability of muscles in response to repetitive nerve stimulation in myasthenia gravis.

BACKGROUND: Repetitive nerve stimulation (RNS) plays an important role in the diagnosis of myasthenia gravis (MG). Technically, this test can be more easily performed on distal muscles than proximal muscles. On the other hand, proximal muscles have been shown to be more easily fatigued or more sensitive than the distal ones. OBJECTIVE: Evaluate the relative fatigability of different muscles in response to RNS in ocular and generalized MG patients. MATERIAL AND METHOD: Two hundred patients with 44 ocular MG and 156 generalized MG were studied The relative fatigability of each muscle was calculated as percentage of cases with abnormal response. A decrement of 10% or more of the amplitude of the compound muscle action potentials was considered abnormal. RESULT: The cases with abnormal response of adductor digiti minimi, anconeus, trapezius, nasalis and orbicularis oculi were 17%, 50%, 55%, 62%, 66% in ocular MG and 53%, 77%, 79%, 85%, 79% in generalized MG respectively. These results showed that in generalized MG the response in all the muscles was more frequently abnormal and was fatigable in a more comparable degree, whereas in ocular MG, the facial muscles were more often abnormal than the limb muscles. CONCLUSION: The abnormal response because of fatigability was more widespread in generalized MG whereas facial muscles were relatively more sensitive in ocular MG. This finding may be useful for the selection of the muscles to be tested in RNS especially in ocular MG.

Polyneuropathy from thiamin deficiency associated with thyrotoxicosis.

Polyneuropathy from thiamin deficiency can occur in persons who consume a diet consisting mainly of polished rice with low protein and thiamin content in the setting of excessive physical activity or hypermetabolic states. The authors report here a 17-year-old fisherman who presented with a 3-month history of symptoms and signs consistent with polyneuropathy. There were also clinical features of thyrotoxicosis which was confirmed by thyroid function test. His dietary intake consisted mainly of polished rice and fish both of which contain a small amount of thiamin. This could not cope with his hypermetabolic condition from thyrotoxicosis resulting in thiamin deficiency with polyneuropathy.

Long-term outcome and factors influencing the outcome of thymectomy for myasthenia gravis.

Thymectomy has gained widespread acceptance as a treatment for patients with myasthenia gravis (MG). Patients with myasthenia gravis who had undergone thymectomy by extended transsternal approach between 1981 and 1987 were retrospectively reviewed to evaluate the result of thymectomy, time to remission, time to maximum improvement and factors influencing remission after thymectomy. There were 128 patients, 45 men and 83 women and the mean ages at the time of thymectomy were 35.7 and 32.2 years respectively. After thymectomy, 41.2% of the patients were in remission, 53% improved and 5.8% had no response. The remission rates at 1, 2, 5 and 10 years after thymectomy were 9%, 17%, 37% and 53% respectively and the median time to remission was 9 years. The maximum improvement rates at 1, 2, 5 and 10 years after thymectomy were estimated to be 30%, 40%, 57% and 78% respectively and the median time to maximum improvement was 3.6 years. Patients with ocular MG, longer duration of symptoms before thymectomy and atrophic thymus gland appeared to take longer to achieve remission although none of the factors was significantly associated with the time to remission. Thymectomy is beneficialfor MG patients with satisfactory remission and improvement rates. It is recommended that thymectomy should be advocatedfor these patients early in the course of the disease because the duration of the symptoms appeared to be the main determinant of the outcome.

Aspergillosis of the central nervous system: a catastrophic opportunistic infection.

The clinical features and outcome of the treatment of aspergillosis of the central nervous system (CNS) in Thai patients are presented. The patients who were diagnosed as having CNS aspergillosis by tissue biopsy or culture from January 1, 1991 to December 31, 2000 were retrospectively reviewed. The study variables including age, sex, underlying disease, symptoms and signs, neuro-imaging studies, pathological findings and outcome of treatment, are described. There were seven cases of aspergillosis of the central nervous system. Four patients were male. The median age was 65 years (range 36-78 years). The most common underlying disease was diabetes mellitus (4/7; 57.1%). Two patients (28.6%) had no underlying disease. The most common primary site of infection was the paranasal sinuses (6/7; 85.7%). The most common clinical presentation was headache (6/7; 85.7%). Common neurological signs included multiple cranial nerve palsies (5/7; 71.4%) and alteration of consciousness (3/7; 42.9%). The median duration of the symptoms prior to admission was 60 days (range 8-180 days). All patients were treated with intravenous antifungal agents at high doses. Extensive surgery was performed in 6 patients. The mortality rate was very high (6/7; 85.7%). The median time from diagnosis and treatment to death was 53 days (22-720 days). Aspergillosis of the CNS should be considered in those with clinical features of headache, multiple cranial nerve palsies and alteration of consciousness accompanied by sinusitis, especially in elderly and diabetic patients. It remains a catastrophic opportunistic infection in spite of the current intensive and aggressive treatment.

Streptococcus suis infection: clinical features and diagnostic pitfalls.

Eight cases of Streptococcus suis (S. suis) infection between 1993-1999 were retrospectively studied. There were 6 cases of meningitis and 2 cases of endocarditis. Acute meningitis with early sensorineural hearing loss was the characteristic feature and the most common presentation of S. suis infection. S. suis endocarditis is a rare presentation in Thailand. This organism was often mistaken for Streptococcus pneumoniae or Streptococcus viridans. In this study, this was true in five cases in whom S. suis was identified later. However, the rapid diagnosis of S. suis meningitis may rely on Gram stain of the CSF in the setting of acute meningitis with hearing loss. These cases were treated with intravenous penicillin or ampicillin with a mean duration of 4 weeks. This treatment was very effective and there was no relapse among these patients.