V Ve en nt ti il la at to or ry y m mu us sc cl le e s st tr re en ng gt th h a an nd d e en nd du ur ra an nc ce e i in n m my ya as st th he en ni ia a g gr ra av vi is s We studied 17 patients with myasthenia gravis (four with ocular involvement alone and 13 with varying degrees of generalized myasthenia gravis). Spirometry, ventilatory muscle strength (maximum inspiratory and expiratory pressures (MIP and MEP)) and endurance (2 min incremental threshold loading test) were measured before and 20 min after i.m. neostigmine. We compared the results with those of 10 normal controls. We found no difference between patients with isolated ocular involvement and controls. Ocular myasthenia gravis patients did not improve after neostigmine. The patients with generalized myasthenia gravis had reduced baseline ventilatory muscle strength (MIP 67 cmH 2 O (70% of predicted), MEP 86 cmH 2 O (50% of pred) and endurance (mean maximal load achieved = 246 g, mean pressure at highest load (P) = 19.4 cmH 2 O) compared with controls. After neostigmine, there was a significant increase in MIP in patients with generalized myasthenia gravis and a trend towards an increased MEP. As a group, the patients with generalized myasthenia gravis did not demonstrate a change in their ventilatory muscle endurance after neostigmine; however, there was considerable interpatient variability in response.We conclude that patients with isolated ocular MG have normal ventilatory muscle strength when tested conventionally. The measurement of ventilatory muscle endurance by incremental threshold loading does not provide additional information to the measurement of ventilatory muscle strength in patients with generalized myasthenia gravis.

The psychostimulant methylphenidate has been previously shown to improve cognitive performance in both normal control volunteers and patient populations. In the present case study, the effects of methylphenidate on cognitive and behavioural function were examined in a single patient with idiopathic normal pressure hydrocephalus (NPH) who had undergone ventriculoperitoneal shunting. A double-blind placebo-controlled ABBA drug design was employed, with the administration of two different doses of methylphenidate followed by neuropsychological assessment on a number of psychometric tests and cognitive tasks drawn from the Cambridge Neuropsychological Test Automated Battery (CANTAB). Methylphenidate produced a dose-dependent positive improvement in behavioural measures in the patient associated with a reduction in apathy. It also had a dose-independent enhancing effect on performance of a Spatial Recognition task. These findings require replication in a large sample of patients to determine whether methylphenidate may prove to be generally useful in enhancing cognition and reducing apathy in normal pressure hydrocephalus.

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