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Occipital epilepsy is characterised by seizures which usually begin with oculomotor or elementary visual symptoms and often spread to other cortical and subcortical regions. We think that the present case report is of particular interest because of the nature of partial status comprising positive (clonic jerks of eyes and left face) and negative motor components (left hemiplegia) with dilatation of the right pupil; these clinical features were shown to be related to a lesion in the right occipital lobe by MRI and EEG. To our knowledge, the association of these data has not been previously reported.
A 37 year old man had a history of chronic renal failure due to an idiopathic mesangiocapillary glomerulonephritis since he was 20 years old. He underwent a renal transplantation which was unsuccessful because of an arterial thrombosis. Two years later, a second kidney was transplanted to the patient. Shortly afterwards, while he was immunosuppressed with steroids and azathioprine, he had aListeria monocitogenes meningoencephalitis. Treated promptly with ampicilline, he had an excellent outcome, except for recurrent generalised seizures due to a residual lesion in the right occipital lobe, shown by CT. The patient was treated with oral 100 mg phenytoin thrice daily and required haemodialysis because of the progressive worsening of his renal function owing to chronic organ rejection. One year later, he was admitted to our hospital because of fever of unknown origin. A few days after admission, he developed a focal status epilepticus characterised by stupor, tonic deviation of the head and clonic jerks of the eyes to the left, full dilatation of the right pupil with sluggish reaction to light, clonic movements of the left face, and left hemiplegia with hyperreflexia and extensor plantar response. No previous clonic movements were seen on plegic limbs. Meanwhile, left pupil responses remained normal. Laboratory studies showed evidence of chronic renal failure and the serum concentrations of phenytoin were 5 μg/ml (reference range 8-20 μg/ml). After intravenous administration of 1000 mg diphenylhydantoin, the seizures stopped and simultaneously the pupillary dilatation disappeared. Thereafter, pupillary assessment showed no abnormalities. A left hemiparesis and extensor plantar response were transient postictal findings. A long TR/ long TE (2000/80) MRI showed a fairly well defined area of hyperintensity on the right occipital lobe, without any sign of a mass effect (figure). Lumbar puncture disclosed a clear CSF under normal opening pressure, with no pleocytosis and containing normal amounts of glucose and proteins; microbiological studies were negative. Several hours after the status had finished, an EEG disclosed sharp spikes and slow waves over the right temporo-occipital region. Fever responded to empirical antibiotic therapy. The clinical course was uncomplicated and the patient continued on phenytoin, being free from seizures after one year of follow up.
Our patient showed a focal status epilepticus with right pupillary dilatation and tonic deviation of the eyes and head to the left; other associated clinical features were clonic movements of the left face and left hemiplegia. All these phenomena disappeared dramatically on phenytoin treatment, thus indicating their epileptic pathogenesis. Although an ictal EEG was not recorded, major although indirect arguments in favour of a right occipitotemporal onset are the interictal EEG spikes as well as the MRI lesion located on that area.
Hemiplegia may be a well known negative ictal phenomenon.1Its association with clonic movements at other levels, as seen in our patient, suggests its ictal mechanism. The absence of previous convulsions on plegic areas further supports that idea. The concomitance of clonic and atonic seizures has only been previously described in a few series and is a very uncommon clinical pattern. However, it is difficult to ascertain that such paresis in this case is directly due to neuronal discharges. Postictal (Todd’s) paralysis may appear in the context of partial status epilepticus, probably due to local fluid changes and this could be another explanation for the hemiplegia in our patient.
Unilateral mydriasis during fits should arouse the suspiction of brain herniation and proper imaging studies should be performed to rule out such a possibility, and that was the case in our patient. Only eight cases with ictal mydriasis have been reported as far as we know. Five patients showed the pupil abnormality contralateral to the epileptic scalp EEG focus and three had ipsilateral mydriasis.2
The exact pathophysiology of pupil changes during seizures remains unclear; it has been stated that miosis would represent an excitatory component3 whereas dilatation would be interpreted as a negative ictal phenomenon.1 Descending inhibition of the Edinger-Westphal nucleus would result in pupillary dilatation and impairment of the pupillary light reflex; this could be mediated by leu-enkephalin fibres which may produce pronounced inhibition of this nucleus in experimental studies.4 Animal experiments performed in macaques showed that electrical stimulation of the anterior occipital lobe produced contralateral ocular deviation with asymmetric dilatation of both pupils that was greater in the homolateral eye5; these features were found in our patient, although we did not see changes in the diameter of the left pupil and the reason for this disparity is unknown. This finding was by contrast with the contralateral mydriasis obtained when the frontal eye field was stimulated5 and in patients with frontal epilepsy. The exact anatomical basis for the changes in pupil diameter during fits remains to be elucidated although the reports and experiments commented on herein, including our case, indicate that an ictal pupil dilatation found in a patient with contralateral epileptic movements suggest occipitotemporal pathology on the same side as the mydriasis; if all these changes are ipsilateral, a frontal lesion should be suspected on the opposite side.