Bilateral mesial temporal polymicrogyria: a case report
- Giorgi Kuchukhidze1,
- Raimund Helbok1,
- Iris Unterberger1,
- Florian Koppelstaetter2,
- Thomas Bodner1,
- Eugen Trinka1
- 1Department of Neurology, Innsbruck Medical University, Innsbruck, Austria
- 2Department of Radiology II, Innsbruck Medical University, Innsbruck, Austria
- Published 2 February 2009
Polymicrogyria is a malformation of cortical organisation morphologically marked by an irregular brain surface with multiple excessively folded small gyri. Cortical thickness is reduced but appears increased in some areas as a result of the fusion of small gyri. On magnetic resonance imaging polymicrogyria is delineated by an abnormal gyral pattern, increased cortical thickness and irregularity of the cortical–white matter junction.
Polymicrogyria is a malformation of cortical organisation morphologically marked by an irregular brain surface with multiple excessively folded small gyri. Cortical thickness is reduced but appears increased in some areas as a result of the fusion of small gyri.1 On magnetic resonance imaging (MRI) polymicrogyria is delineated by an abnormal gyral pattern, increased cortical thickness and irregularity of the cortical–white matter junction.2
Clinical presentation largely depends on the localisation of polymicrogyria and the extent of cortical involvement. Several topographically distinct syndromes of bilateral polymicrogyria have been described.2 Polymicrogyria may be the result of acquired intrauterine insults (ischaemia, twinning, infections with cytomegalovirus, toxoplasma, varicella-zoster virus) as well as inherited (familial polymicrogyria syndromes) or metabolic disorders (Leigh syndrome, Zellweger syndrome).1
A 26-year-old right-handed man was referred to the video-electroencephalographic monitoring unit for presurgical evaluation of medically intractable epilepsy. The patient was born after an uneventful pregnancy and delivery. His developmental milestones were age relevant and he attended a regular school. His epilepsy manifested at the age of 17 years with epigastric auras, reaching a maximum frequency of several auras per week. One year later the epigastric auras were followed by secondary generalised tonic–clonic seizures with a marked postictal confusion. Routine electroencephalography (EEG) was abnormal with intermittent bitemporal slowing; cerebral computed tomography at that time was reported as normal. The patient was diagnosed with temporal lobe epilepsy and was seizure free for seven years on monotherapy with carbamazepine and later with oxcarbazepine. At the age of 25 years his seizures resumed. At this stage MRI showed bilateral symmetrical mesial temporal polymicrogyria with thickened cortex in the hippocampal and parahippocampal areas bilaterally, best seen on coronal T2 (3 mm slice thickness) and axial T2 (2 mm slice thickness) images. The grey–white matter interface was irregular and the normal morphology of both hippocampi was distorted. The temporal horns of the lateral ventricles were enlarged bilaterally. White matter was normal and there were no associated abnormalities observed on cerebral MRI (fig 1).
The neurological examination of the patient was normal. Neuropsychological testing showed an IQ of 118, intact frontal executive functions and significantly impaired verbal and non-verbal memory (Munich memory test, verbal and non-verbal learning tests). During the prolonged video-electroencephalographic monitoring two secondary generalised tonic–clonic seizures were recorded, with a motionless stare, deviation of the eyes and head to the left, stretching and dystonic posturing in the left upper extremity followed by generalised tonic–clonic activity, with the last clonic jerking in the right arm. Ictal EEG showed rhythmic theta activity in the right mesial temporal area followed by regional spreading and generalisation of the ictal activity. Postictal confusion lasted several minutes. On interictal EEG repetitive sharp waves were recorded in the right mesial temporal region. There was no epileptiform activity on the left side. Clinical and EEG findings suggested the diagnosis of right-sided mesial temporal epilepsy.
The patient had a remarkable family history of epilepsy. He was the only child of unrelated parents. His mother reported no stillbirths or miscarriages. The mother had temporal lobe epilepsy, her MRI showed an unspecific gliotic lesion in the left thalamus and her neurological examination was normal. The patient’s father had had febrile seizures in childhood; he never underwent neuroimaging. The patient’s maternal grandmother had seizures manifested in her sixties; she took some anticonvulsants, but further information was unavailable. The patient’s maternal grandfather’s sister had had epileptic seizures in her childhood and adolescence; she took medication and has been seizure free since her late thirties. Neither the grandmother nor the grandfather’s sister underwent neuroimaging.
Polymicrogyria most commonly involves the perisylvian region (80–85% of patients).3 Generalised polymicrogyria or isolated frontal, temporal lateral or occipital polymicrogyria are relatively infrequent. In a large series of patients with polymicrogyria, the hippocampus along with the striate cortex, gyrus rectus and cingulate gyrus were not affected.3 In general, developmental malformations affecting hippocampal formation are rare.4 Bilateral mesial temporal polymicrogyria was not previously reported.
Topography of polymicrogyria is in accordance with its clinical presentation. Patients with bilateral perisylvian polymicrogyria typically have difficulties with palatal and tongue movements and speech delay. Bifrontal polymicrogyria causes spastic tetraparesis, delayed motor and language milestones and mental retardation. Patients with extensive polymicrogyria involving different cortical regions have the most severe clinical presentation.2 Our patient presented clinically with mesial temporal epilepsy and significant memory deficit, which is in line with the localisation of the patient’s polymicrogyria.
Approximately 50% of patients with polymicrogyria have epilepsy.2 They are rarely good candidates for epilepsy surgery because epileptogenic zones frequently involve eloquent cortical areas. Conversely, bilateral mesial temporal abnormalities, such as hippocampal sclerosis, do not necessarily contraindicate epilepsy surgery. These patients usually undergo a thorough presurgical work-up including EEG recording with intracranial electrodes and if the epileptogenic zone is located unilaterally the surgical outcome is likely to be favourable. In our patient the epileptogenic zone was presumed to be in the right mesial temporal area (by clinical presentation, ictal and interictal scalp EEG), although he was not yet considered for epilepsy surgery because of the good response to recently administered levetiracetam and his previous temporary remission for 7 years.
The majority of reported cases of polymicrogyria are sporadic and one of the main causes is intranatal ischaemia.1 The perisylvian cortex, the most commonly affected by polymicrogyria, is in the distribution of the middle cerebral artery, although the patterns of polymicrogyria are not always parallel to the classic vascular irrigation zones. Our patient was born after an uneventful pregnancy and labour and it is unlikely that the cause of his polymicrogyria could be an intranatal hypoxic event. There was also no evidence of any intrauterine infection or metabolic disorder.
A positive family history of epilepsy (14%) or malformation of cortical development (17%) is not rare in patients with polymicrogyria.5 Our patient had a positive family history of epilepsy. The mother of the patient did not have a malformation of cortical development on cerebral MRI. The other family members, either those with epilepsy or without, never underwent neuroimaging. It remains speculative whether the rare type of polymicrogyria in our patient could be familial.
Polymicrogyria is a malformation of cortical organisation morphologically marked by an irregular brain surface with multiple excessively folded small gyri.
Polymicrogyria can result from in utero, inherited or metabolic causes.
A case of bilateral temporal lobe polymicrogyria is reported which presented clinically with mesial temporal epilepsy and significant memory deficit.
This article has been adapted with permission from Kuchukhidze G, Helbok R, Unterberger I, Koppelstaetter F, Bodner T, Trinka E. Bilateral mesial temporal polymicrogyria: a case report. J Neurol Neurosurg Psychiatry 2008;79:483–4.