Transient postictal blindness after a focal posterior cingulate gyrus seizure

1. Introduction

Blindness is a rare postictal manifestation, that has been reported following generalized seizures or focal mostly occipital epilepsy primarily in children [1] but also in adults [2]. We report the case of a man with medically-refractory epilepsy who developed new transient postictal blindness following a prolonged cingulate gyrus focal seizure.

2. Case report

A 26-year-old right-handed man with medically refractory focal epilepsy was admitted to our service for long-term video-EEG monitoring (LTM) with subdural electrodes. His first seizure was at the age of seven years. Despite being compliant with levetiracetam 2000 mg twice daily and topiramate 200 mg twice daily, he was having an average of one generalized tonic-clonic seizure, usually during sleep, and two focal seizures per week. His focal seizures were typically heralded by an occipital headache described as a feeling of pressure and lasting usually less than 30 min, followed by repetitive bilateral upper extremity movements, sometimes progressing to asymmetric tonic posturing, typically lasting under a minute with varying degrees of impaired awareness. Seizure triggers based on subjective historical information, included sleep deprivation, consumption of excess salty foods and exposure to temperature extremes. His medical history was otherwise unremarkable. Family history was positive for a maternal aunt who had epilepsy. Social history was noncontributory. Neurological examination was normal.

Phase I LTM showed rare left fronto-temporal slowing and no definite interictal epileptiform discharges. Ictal EEG during some seizures showed left hemispheric rhythmic delta slowing with subsequent obscuration by muscle artifact. A high-resolution epilepsy protocol 3T brain MRI and subsequently a 18 F-fluorodeoxyglucose PET were unremarkable. Phase II monitoring was performed, with bilateral intracranial electrode placement: a left frontal craniotomy was done for insertion of grid and strip electrodes inter-hemispherically and to cover the left frontal lobe; strip electrodes were inserted through a right frontal burr hole. Interictal EEG revealed frequent runs of low amplitude spike or polyspike and slow wave in the left inter-hemispheric electrodes close to the cingulate gyrus. During monitoring he had two typical seizures, characterized by arousal from sleep, followed by asymmetric tonic posturing of the upper extremities, with the left elbow flexed and right elbow extended and accompanied by vocalizations, which resolved within 3 min. Ictal EEG showed brief continuous spiking at the left posterior interhemispheric electrodes with rapid anterior spread before resolution. After one week of monitoring, to better localize the seizure focus, two depth electrodes were placed into the cingulate gyrus with repositioning of the interhemispheric posterior cingulate strip electrodes for additional coverage (Fig. 1A).

Fig. 1.

(A) Pre-operative T1-weighted brain MRI sequence co-registered with post-implantation CT showing LPMIH2 electrode (blue arrow) and LMCD depth electrode in close proximity (yellow arrow). (B) Ictal EEG recorded with subdural electrodes demonstrating seizure onset in the posterior interhemispheric electrodes (LPMIH2) with rapid spread to the depth electrodes in the cingulate gyrus (LMCD2). (C) Axial T1-weighted sequences from post-operative brain MRI, showing the focal area of resection in the medial left frontal lobe (cingulate gyrus). (D) H&E stained section shows scattered ballooned/dysplastic neurons in the white matter (arrows), consistent with a diagnosis of focal cortical dysplasia type IIB; magnification @100×.

In the evening after surgery, the patient had a typical focal seizure with similar semiology to prior events but not preceded by headache. Dystonic posturing of the upper extremities lasted for four minutes but he did not fully regain consciousness. Five minutes later, he became tachycardic, had lip smacking and recurrent bilateral tonic posturing of the upper extremities, which resolved after administration of lorazepam 2 mg IV and fosphenytoin 2000 mg IV. Total duration of the seizures was approximately 15 min. Soon after, the patient reported that he could not see a family member by his bedside. He had never experienced this before and denied any other neurological symptom. On examination, he was tachycardic with the rest of his vitals normal, his pupils were equal, round and reactive to light and extraocular muscles were intact, but he denied any light perception with either eye and was not blinking to threat. His optic discs appeared sharp with no evidence of papilledema. Otherwise, his cranial nerves were intact and he had normal tone, power, reflexes and sensation in all four extremities. Ictal EEG showed onset of the seizure again in the posterior interhemispheric electrodes with rapid spread to the depth electrodes in the cingulate gyrus (Fig. 1B).

An urgent MRI/MRA/MRV of his brain showed typical post-operative changes but no evidence of stroke or occipital lobe pathology. Ten hours later the patient reported some recovery with the ability to identify certain colors and discerning the outline of objects. At this point, his light-perception had recovered and he could track moving objects, but was unable to identify them. By forty-eight hours after the seizures, his vision had fully recovered to baseline: he could read and identify objects.

After capturing several typical seizures with LTM, onset was localized to the left posterior cingulate gyrus and small portion of the adjacent supplementary motor area (SMA). Surgical resection of the foci has since resulted in no further seizures during initial 5-months follow-up, and he has recovered well from SMA syndrome. Post-operative MRI is shown in Fig. 1C. Histological analysis of the resected tissue revealed focal cortical dysplasia type IIB (Fig. 1D).

3. Discussion

Postictal blindness has been primarily described in children following generalized and focal occipital seizures [1]. In the fewer reported adult cases, postictal blindness has been reported in association with focal occipital seizures, but more commonly generalized seizures, with patients often in denial of their objective blindness (Anton’s syndrome) [3]. Our patient’s ictal intracranial EEG recordings revealed a seizure focus in the posterior cingulate gyrus with pathological findings consistent with focal cortical dysplasia in this region. Our case was unusual in that our patient did not demonstrate Anton’s syndrome and he had never had any visual impairment associated with his seizures before. It is our thinking that his focal extra-occipital seizure propagated to both occipital lobes, although this remains hypothetical since no electrodes were placed in the occipital regions. Another limitation is the lack of visual evoked potentials at the time of blindness.

We considered the possibility of an adverse drug effect being responsible for the blindness, however lorazepam and phenytoin have only been reported to cause blurred vision and xanthopsia [4]. In addition, the temporal onset of the symptoms postictally, as well as the gradual improvement without other specific treatment supports a postictal etiology.

Our case demonstrates that complete postictal blindness can newly occur after focal extra-occipital seizures in adult patients with epilepsy without any prior history of seizure-related visual disturbances. This rare phenomenon remains a diagnosis of exclusion.