7207Journal of Neurology, Neurosurgery, and Psychiatry 1992;55:720-722 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.55.8.720 on 1 August 1992. Downloaded from SHORT REPORT Hemimegalencephaly and normal intellectual development Lucia Fusco, Stefano Ferracuti, Giuseppe Fariello, Mario Manfredi, Federico Vigevano Abstract disability. His parents (who were unrelated) Hemimegalencephaly is a rare congenital and sister and brother were in good health. Bambino Gesu malformation characterised by over- When he was 14 years 5 months old, brief Children's Hospital, repetitive jerks developed National Medical growth of one hemisphere. Although it is episodes of sudden Research Institute, commonly thought to be associated with in the left arm; these attacks occurred mostly Rome neurological deficits, developmental after awakening and recurred daily. A month Section of delay, and intractable epilepsy, the clinical later he was admitted to hospital because one Neurophysiology can such episode was followed by a tonic-clonic L Fusco expression of hemimegalencephaly, vary widely. This patient was neurologi- seizure. A CT scan obtained on admission (fig F Vigevano a pathological right hemi- Department of cally and neuropsychologically normal A) demonstrated Radiology apart from rare partial seizures. sphere, which appeared increased in size, with G Fariello high lucency of the white matter. This was La Sapienza (J Neurol Neurosurg Psychiatry 1992;55:720-722) interpreted as oedema of the right lobe and University, Rome, despite his normal neurological condition the Italy Hemimegalencephaly is a congenital cerebral patient was treated with high doses ofmannitol Department of He was discharged on a Psychiatry and abnormality consisting of unilateral hyper- and corticosteroids. Medical Psychology trophy of the brain. Most patients with hemi- regimen of phenobarbitone. S Ferracuti megalencephaly present with contralateral Three months later he was referred to us for Department of hemiparesis, mental retardation, and refrac- further investigation. On admission, his neuro- Neuroscience Unlike most reported logical status was normal. Neither somatic M Manfredi tory partial epilepsy. cases, our patient was otherwise neurologically hemihypertrophy nor skin lesions were evident. Correspondence to: the normal Dr Vigevano, Section of normal. Biochemical findings were within Neurophysiology, Bambino range. Analyses of CSF were normal. Sensory Gesu Children's Hospital, National Medical Research conduction in the left ulnar and sural nerves, Institute. Piazza S Onofrio 4, Case report visual evoked potentials and somatosensory 00165 Rome, Italy The personal and neurological history of this evoked potentials to right limb stimulation Received 8 July 1991 and in to revised form 19 year old patient was normal; pregnancy and were all normal, but the evoked potentials 2 September 1991. He had a normal left limb stimulation were abnormal. Cortical birth were uncomplicated. http://jnnp.bmj.com/ Accepted 10 September left common 1991 psychomotor development and no learning response to stimulation of the on September 24, 2021 by guest. Protected copyright. Note the diffusely hypodense right white matter. B) Coronal SE 19941100 MRI shows a Figure A) Axial CT scan shows an enlarged right hemisphere. appear moderate enlargement of right hemisphere, increase in white matter, with prolonged T2 relaxation time; at this frontal level cortical gyri and suki normal. C) Axial IR 1615130 MRI through basal ganglia shows abnormal gyral pattern in posterior temporal region. Note that in B) and C) the straightening of right frontal horn of lateral ventricle which is characteristic of hemimegalencephaly. (In all figures the right side of the brain is on the left of the figure). Hemimegalencephaly and normal intellectual development 721 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.55.8.720 on 1 August 1992. Downloaded from peroneal nerve was absent and response to crogyria or polymicrogyria. Barkovich and stimulation of the left median nerve was Chuang did not attempt to correlate the delayed and decreased in amplitude. Transcor- anatomical appearances of their patients with tical magnetic stimulation showed normal the clinical features. Our patient had over- pyramidal conduction on both sides. EEGs growth of one hemisphere, in which the white showed fast beta rhythms in the right frontal matter was increased and had prolonged T2 and central regions, with frequent spike and relaxation time on MRI. Unlike Barkovich's spike-and-wave complexes in wakefulness and patients, the cerebral cortex conformed to an sleep. Seizures recorded on video and EEG altogether different pattern: the frontal, anter- were characterised clinically by brief, arrhyth- ior temporal and parietal lobes had normal gyri mic muscle jerks in the left arm, accompanied and sulci. The marked abnormalities affected electrically by right frontal spike-and-wave only a small area ofthe posterior, temporal and complexes that became bilateral. parietal lobes. In our opinion, the preservation The results of neuropsychological tests were of normal cortex largely explains the patient's normal; the patient had an IQ of 115. MRI normal neuropsychological status. We (figs B and C) demonstrated overgrowth of the observed that the neuromental development in right hemisphere, which was 1 2 times larger hemimegalencephaly is notably worse in than the left. The right hemispheric white patients with more pronounced agyria or matter was increased and had a prolonged T2 pachygyria7 and probably correlates with the relaxation time. The cortical gyri and sulci in cortical pattern of malformation. Routine the frontal, anterior temporal, and occipital neurophysiological studies, including magnetic regions appeared normal. In the posterior transcranial stimulation and visual evoked temporal and parietal regions the grey matter potentials, confirmed the integrity of the cen- was slightly increased in size, with multiple tral and occipital regions. Abnormal right macrogyri. The grey-white matter junction was somatosensory evoked potentials to contra- distinct in this area only. lateral limbs corroborated anomalies in the Although phenobarbitone and carbamaze- parietal cortex. The normal neuropsychologi- pine failed to control the seizures, they dis- cal testing results also demonstrated the integ- appeared with valproate and have not recurred. rity of higher symbolic functions. It is unclear The patient's current neurological examina- why the abnormal MRI white matter signal tion confirms the absence of abnormalities. He was not expressed clinically. is now working as an office machine techni- Stable left lateralisation (contralateral to the cian. Recent EEGs show less paroxysmal hemimegalencephaly) and arm localisaton activity: this now occurs only during hyper- characterised our patient's seizures. They ventilation and sleep. The fast beta rhythm is manifested with single arrhythmic jerks of still present in the central and parietal regions. variable frequency and amplitude involving A second battery of neuropsychological tests, different muscle groups. This seizure pattern given four years after the first, showed a verbal differs from the partial motor seizures of IQ of 1 3 and a performance IQ of 1 4; rolandic origin, which are rhythmic, localised visuospatial and superior cognitive functions in one muscle group alone or successively were normal. involve more groups according to the somato- topic distribution of the cerebral cortex. It is, http://jnnp.bmj.com/ however, typical of focal cortical myoclonus, Discussion earlier reported in association with contra- Hemimegalencephaly is a dysplastic lesion lateral focal pericentral lesions (tumour or characterised by an overgrowth of one hemi- cicatrix) or contralateral atrophy, as seen in sphere. The cerebral cortex of the megalence- infantile hemiplegia.8 More recently, Kuz- phalic hemisphere is generally abnormal and niecky et al,9 have described focal cortical commonly has large pachygyric areas, at times myoclonus in three patients, who had focal associated with polymicrogyria. The white dysplastic lesions, such as central macrogyria. on September 24, 2021 by guest. Protected copyright. matter is also abnormal. The neuroimaging Apart from the epileptiform abnormalities, features of hemimegalencephaly have been the EEGs of our patient were characterised by adequately described.`3 Mental retardation right central and parietal beta activity of low and contralateral hemiparesis are generally voltage. Patients with neuronal migration associated with early epilepsy that is highly anomalies typically exhibit fast background resistant and at times mandates surgery; the rhythms'0 consisting of continuous alpha and treatment usually chosen is hemispherec- beta activity. In bilateral malformations such as tomy.45 Nevertheless patients with slight men- lissencephaly the activity is widely distributed tal retardation and non-refractory epilepsy over the two hemispheres; in focal dysplastic with minimal neurological signs and without lesions it is lateralised or localised. epilepsy have been observed.6 The clinical expression of hemimegalencephaly thus varies 1 Kalifa GL, Chiron C, Sellier N, et al. Hemimegalencephaly: widely. A similarly wide variation also appears MR imaging in five children. Radiology 1987;165:29-33. likely in the anatomical lesions.7 2 Osborn RE, Byrd SE, Naidich TP, Bohan TP, Friedman H. MR imaging of neuronal migrational disorders. Am J In describing