Afferent and efferent excitabilities of the transcortical loop in patients with dentatorubral-pallidoluysian atrophy

Neuropathological analysis of the brainstem and cerebral cortex lesions on epileptogenesis in hereditary dentatorubral-pallidoluysian atrophy

In order to investigate epileptogenesis in hereditary dentatorubral-pallidoluysian atrophy (DRPLA), we immunohistochemically examined the expression of neurotransmitters, neuropeptides, calcium-binding proteins and/or glutamate transporters in the brainstem and cerebral cortex in autopsy cases. The subjects comprised 14 cases of clinicopathologically confirmed DRPLA, including 7 cases of juvenile and 2 cases of early adult types with progressive myoclonus epilepsy (PME), 5 cases of late adult type without PME, and 10 age-matched controls. Serial sections of the brainstem and cerebral cortex were treated with antibodies to tyrosine hydroxylase, tryptophan hydroxylase, substance P, methionine-enkephalin, parvalbumin, calbindin-D28K, calretinin, and excitatory amino acid transporters. Although the size of the tegmentum was small, we failed to find any PME-specific brainstem changes in the expression of neurotransmitters, neuropeptides and calcium-binding proteins. The number of interneurons immunoreactive for calbindin-D28K and parvalbumin, markers of GABAergic inhibitory interneurons, were reduced throughout the cerebral cortex, but there was no significant difference in the density of immunoreactive neurons between DRPLA patients of each type. The expression of glutamate transporters was comparatively spared. The current study revealed an absence of PME-specific brainstem lesions and indicated a possible involvement of the reduced GABAergic interneurons in the cerebral cortex in formation of PME in DRPLA.

Seizure incidence during single- and paired-pulse transcranial magnetic stimulation (TMS) in individuals with epilepsy

OBJECTIVE

We reviewed published data and our own data to determine a quantitative incidence of seizure in subjects with epilepsy undergoing single- and paired-pulse transcranial magnetic stimulation (spTMS and ppTMS) and to explore conditions that may increase this risk.

METHODS

A PubMed literature search was performed, and articles from this search were reviewed. Subjects from our institution also were included.

RESULTS

The crude risk of a TMS-associated seizure ranges from 0.0 to 2.8% for spTMS and 0.0-3.6% for ppTMS. Medically intractable epilepsy and lowering antiepileptic drugs were associated with increased incidence. There was significant center-to-center variability that could not be explained by differences in patient population or by differences in reported stimulation parameters. In all cases, seizures were similar to each subject's typical seizure and without long-term adverse outcome. In most cases, doubt was expressed in the original reports as to whether the seizures were induced by TMS or merely coincidental.

CONCLUSIONS

The incidence of seizure in a subject with epilepsy during spTMS and ppTMS appears to be small and not associated with long-term adverse outcome. The incidence is higher under the specific conditions mentioned above.

SIGNIFICANCE

These findings may enable researchers to more accurately inform subjects of seizure risk during TMS.