Periventricular nodular heterotopia and childhood absence epilepsy

Genetic generalized epilepsies with frontal lesions mimicking migratory disorders on the epilepsy monitoring unit

Objective

Some patients with genetic generalized epilepsy (GGE) may present with ambiguous and atypical findings and even focal brain abnormalities. Correct diagnosis may therefore be difficult.

Methods

We retrospectively collected six patients investigated on the epilepsy monitoring unit with MRI abnormalities mimicking focal cortical dysplasia (FCD-like) or heterotopias, but with semiology and EEG features of GGE. We compared them to four additional patients with GGE and nonmigratory abnormalities.

Results

All six patients presented with frontal MRI lesions: radial ("transmantle," n = 4), cortical-subcortical (n = 1), and periventricular heterotopia (n = 1). Five had positive family histories. Semiologic lateralizing signs compatible with the lesion were seen in four. Five patients had 3/s spike-wave complexes, with an asymmetric appearance in three. Regional EEG changes matched with the side of the abnormality in three patients. Invasive EEG (n = 2) or postoperative outcomes (n = 3) argued against an ictogenic role of the MRI abnormalities. Histology showed mild malformation of cortical development, but no focal cortical dysplasia. The six patients were finally diagnosed with juvenile myoclonic epilepsy (n = 2), juvenile absence epilepsy (n = 2), or GGE not further specified (nfs, n = 2). Compared to these patients, the other four (final diagnoses: childhood absence epilepsy, n = 1; perioral myoclonia with absences, n = 1; and GGE nfs, n = 2) had no lateralizing EEG findings.

Significance

Patients with GGE may have coincidental MRI abnormalities. These cases are challenging as frontal epilepsy and GGE can present with similar semiologies. GGE with coincidental FCD-like lesions/heterotopias is in particular difficult to diagnose as patients have more lateralizing features (in semiology and EEG) than those with tumors. A detailed noninvasive presurgical evaluation may be justified. We point out red flags that may help to distinguish GGE from frontal epilepsy, even in the presence of brain abnormalities: 3/s spike waves (even if asymmetric), changing lateralizing signs at different times, and a positive family history hinting at GGE.

Absence epilepsy and periventricular nodular heterotopia

We report a case of a girl who presented with typical absence seizures at age of 4.5 years. EEG showed absence seizures of sudden onset with 3 Hz spike-and-waves that also correlated with the clinical absences. The seizure semiology included subtle deviation of the eyes which prompted MRI investigation of the brain. This showed a periventricular nodular heterotopia in the mid to anterior horn of the right lateral ventricle. Although possibly coincidental, periventricular heterotopia are considered to be epileptogenic and this association has been reported once before. Migration disorders, such as in the periventricular heterotopia of our patient, may influence the formation and excitability of the striato-thalamo-cortical network involved in the generation of 3 Hz spike-waves.

Use and Abuse of EEG in the Diagnosis of Idiopathic Generalized Epilepsies

This article concentrates on the role of electroencephalograms (EEGs) in the diagnosis and management of patients with idiopathic generalized epilepsies (IGEs). We review the morphologic and behavioral characteristics of the interictal and ictal EEG markers of IGE that should guide recording strategies to augment its diagnostic yield, and we attempt to delineate those particular features that may be relevant to different IGE syndromes. We also explore the electrographic boundaries between IGEs and cryptogenic/symptomatic generalized and focal epilepsies, and focal/secondary generalized epilepsies, with particular relevance to the phenomena of focal abnormalities and secondary bilateral synchrony, commenting on possible diagnostic pitfalls and areas of uncertainty.

A child with Friedreich's ataxia and epilepsy

Epilepsy in Friedreich's ataxia is rare. We describe a 9-year-old boy with Friedreich's ataxia who had onset of symptoms in the second year of life and developed a generalized epilepsy at age 5 years. On cerebral magnetic resonance imaging, he has a subependymal gray-matter heterotopia. We suggest that his gray-matter heterotopia might be related to his diagnosis of Friedreich's ataxia and that his early onset of symptoms might be related to the length of his guanine-adenine-adenine (GAA) triplet repeat expansion.

Clinical features and long term outcome of epilepsy in periventricular nodular heterotopia. Simple compared with plus forms

OBJECTIVES

Little is known about the long term outcome of patients with periventricular nodular heterotopia (PNH) and epilepsy, particularly the course of seizures. This study investigated the electroclinical and prognostic features of 16 patients with PNH.

METHODS

Of 120 patients with epilepsy and malformations of cortical development, 16 had PNH. Of these, eight patients had periventricular nodules only (simple PNH) and eight also presented with other cortical or cerebral malformations (subcortical heterotopia; polymicrogyria; focal dysplasia; schizencephaly; cortical infolding; agenesis of the corpus callosum; mega cisterna magna and cerebellar atrophy) (PNH plus). All patients underwent clinical, neurophysiological, and MRI investigation. The mean follow up was 17.3 years (2-40 years).

RESULTS

Two electroclinical patterns emerged: (1) The first pattern, associated with simple PNH, was characterised by normal intelligence and seizures, usually partial, which began during the second decade of life. The seizures never became frequent and tended to disappear or become very rare. The EEG showed focal abnormalities. (2) The second pattern, associated with PNH plus, was characterised by mental retardation and seizures that began during the first decade of life. The seizures were very frequent in most cases and sudden drops were observed in six patients. Seizures were medically refractory in four patients. The EEG showed focal and bisynchronous abnormalities.

CONCLUSIONS

Two groups of PNH patients with different electroclinical and neuroradiological features can be identified after a long term follow up. The presence of other types of cortical or cerebral malformations, in addition to periventricular nodules, determines a poor prognosis.