Parkinsonism and epilepsy

Progressive Supranuclear Palsy

Progressive supranuclear palsy (PSP) was first recognized as a distinct morbid entity by Richardson, Steele and Olszewski a quarter century ago. Subsequent experience has confirmed and extended their original observations. PSP has become familiar as a chronic progressive disorder with extrapyramidal rigidity, bradykinesia, gait impairment, bulbar palsy, dementia and a characteristic supranuclear ophthalmoplegia. It is an important cause of parkinsonism. Its etiology remains obscure. Familial concentrations have not been observed.

Some cases exhibit no oculomotor dysfunction. Dementia is usually mild. Recent neuropsychological studies have defined features consistent with frontal lobe cortical dysfunction. Seizures and paroxysmal EEG activity may occur.

CT and MRI scans show midbrain atrophy early and later atrophy of the pontine and midbrain tegmentum and the frontal and temporal lobes. PET scans have shown frontal hypometabolism and loss of striatal D-2 dopamine receptors. Postmortem studies have documented involvment of both dopaminergic and cholinergic systems. Treatment remains palliative and unsatisfactory.

Paradoxical anticonvulsant activity of the gamma-aminobutyrate antagonist bicuculline methiodide in the rat striatum

Bicuculline methiodide (BMI), a gamma-aminobutyrate (GABA) antagonist, is a powerful convulsant agent when injected into the cerebral ventricles, amygdala, hippocampus, thalamus, neocortex, and deep prepiriform cortex in rats. In contrast, bilateral microinjection of BMI into the rat striatum confers protection against seizures induced by the cholinergic agonist pilocarpine (380 mg/kg, i.p.), with an ED50 of 94 fmol (range 45-195 fmol). No topographical variation in the anticonvulsant action of BMI was detected throughout rostrocaudal and dorsoventral aspects of the striatum. The anticonvulsant action of BMI in the striatum was reversed by coadministration of the GABA agonist muscimol or by blocking GABA-mediated inhibition in either the substantia nigra pars reticulata or in the entopeduncular nucleus. The results show that blockade of GABA-mediated inhibition in the striatum has a powerful anticonvulsant effect in the pilocarpine model, suggesting that GABAergic transmission in the striatum modulates the seizure propagation in the forebrain.

Tourette syndrome, an acquired encephalopathy? A report of two cases with epileptiform dysrhythmia

The electroencephalogram, although providing no specific diagnostic information for Tourette syndrome, may be useful in evaluating the pathology in which the syndrome occurs, since it appears that at least some cases may occur in the setting of an underlying acquired encephalopathy of diverse etiology. A neurochemical basis for the Tourette syndrome expressed as an extrapyramidal circuit imbalance may also relate to a discharge threshold for epileptiform activity. A more detailed electroencephalographic evaluation of such patients using nasopharyngeal or sphenoidal recording may be useful in this regard.