Parietal and occipital seizures have long been considered rare. In part, the rarity may be due to the diagnostic challenge they present. Parietal and occipital seizures have variable clinical presentations with combinations of positive and negative somatosensory and visual symptoms that may be mistaken for migraine or ischemic events (1-4). In some cases, patients with occipitoparietal epilepsy may develop an ictal or postictal amaurosis or hemianopic visual field defects. The underlying etiology for these seizures in adult populations may be due to a vascular lesion, neoplasm, demyelination, trauma, anoxia, or posterior reversible encephalopathy syndrome. We present a case of new-onset occipitoparietotemporal seizures leading to a reversible homonymous hemianopia in which no underlying cause was found.
A 34-year-old woman with a history of ulcerative colitis and primary sclerosing cholangitis was admitted for elective liver transplantation. On hospital day 2, the patient had surgery without any complications. Postoperatively she was started on mycophenolate mofetil, tacrolimus, and prednisone for immunosuppression.
On postoperative day (POD) 8, the patient complained of spells of changes in her vision. The spells began with a sensation of vertigo, followed by spots of light or “sparkles” on the right side of her binocular peripheral vision. She was then overcome by a cold chill followed by a hot flash. The entire episode would last for less than 2 minutes and would occur between 5 and 20 times per day. Over the next 3 days, she began experiencing complex visual hallucinations. In addition to phosphenes, she would see false images of nurses walking along her right side as if they were coming to fix her intravenous line. There was no auditory component to these hallucinations, and the patient was aware that these images were not real.
On POD 13, she reported decreased peripheral vision on her right side and an intermittent, throbbing, left temporal headache. Her neuro-ophthalmologic examination revealed visual acuities near 20/20 bilaterally with normal pupillary responses, full extraocular movements, and unremarkable funduscopic exam. Automated perimetry demonstrated a right homonymous hemianopia with macular sparing (Fig. 1A). The remainder of her physical exam was unremarkable.
The etiology for the patient's hemianopia was unclear. She had no personal or family history of seizures. Vital signs, serum electrolytes, and liver function tests were normal, and tacrolimus levels were within therapeutic range. Brain MRI with and without contrast was unremarkable. Despite the lack of radiological or serological evidence suggesting tacrolimus neurotoxicity, the patient's tacrolimus was discontinued and replaced with cyclosporine on POD 15. There was no immediate improvement in her symptoms following this change of medication.
Video electroencephalogram (EEG) monitoring on POD 15 revealed 22 events within a 24-hour period. These consisted of simple partial seizures originating in the left occipitoparietotemporal head regions with maximal surface negative discharges recorded from the occipital electrodes. The ictal activity rapidly spread to the immediate parietal and temporal leads but remained confined to electrodes P3-O1 and T5-O1 with no secondary generalization. Clinically, the patient had a right gaze deviation with brief eyelid fluttering at the seizure onset. She then described phosphenes and complex visual hallucinations of people walking in her right visual field, followed by sensations of cold chills and hot flashes rising in her upper body. She remained conscious and coherent throughout each event. The EEG and clinical presentation were consistent, lasting about 140 seconds (Fig. 2). Interictally, she complained of a persistent right homonymous hemianopia.
The patient was started on 500 mg oral levetiracetam twice daily on POD 15 but continued to have seizure activity. By POD 16, the levetiracetam increased to 1,000 mg twice a day, and no further epileptiform activity was recorded. The patient also reported a cessation in her visual hallucinations, although her hemianopia persisted. However, by POD 19, the patient had complete resolution of her hemianopia (Fig. 1B).
Our patient had frequent cryptogenic occipitoparietotemporal simple partial seizures that resulted in ictal and postictal right homonymous hemianopia with macular sparing. This case demonstrates several classic clinical findings associated with parietal and occipital seizures. For example, eyelid fluttering is a known presentation in occipital seizures (1,5). Elementary visual hallucinations of phosphenes are also common in occipital seizures, particularly when seizure discharges originate from the lateral convexity of the occipital lobe (1). Typically, the phosphenes of occipital seizures are described as multicolored circles or spots, but as with our patient, some have reported achromatic flashing lights as well (3,4). The location of ictal phosphenes is classically in the contralateral hemifield. In 18 patients with occipital epilepsy reported by Panayiotopoulos (3), 13 patients characterized their elementary hallucinations to be located in the contralateral, monocular, temporal hemifield. Although our patient also experienced phosphenes in the contralateral hemifield, she distinctly described it as a binocular phenomenon.
The formed visual hallucination that our patient described, that is, seeing people moving from the periphery to the midline of her hemianopic field, is a characteristic example of complex visual hallucinations associated with occipitoparietal seizures. As with our case, patients with complex ictal hallucinations frequently have a gaze preference in the direction of the hallucination but are usually aware that their hallucinations are not real (1).
During the final moments of her epileptic events, our patient reported thermal fluctuations. Thermal sensations, although less common than other sensory findings of pain or paresthesias, have been observed in occipitoparietal seizures. Prior studies suggest that fluctuation in thermal perception may originate from the perisylvian region (1). However, in our patient, the thermal fluctuations did not correlate with a perisylvian electrographic spread pattern.
In this case, all of the events were brief and were followed by postictal headaches, both of which are common features of occipital seizures (3,4). Our patient also experienced ictal and postictal right homonymous hemianopia with macular sparing. Her postictal EEG showed brief delta activity, most prominently in the left temporal lobe. Postictal hemianopia, a type of Todd's phenomenon, has been previously reported (2,6,7). In this case, our patient had macular sparing of her visual field. Although macular sparing would suggest an isolated occipital ictus, the EEG demonstrated that she had an occipitoparietal ictus. This discrepancy may be secondary to the limited sensitivity of scalp leads, which may not record the weaker electrical field of simple partial seizures. Given the maximum negativity over the O1 electrode, it is possible that our patient's seizure originated in the occipital lobe but was better detected by the scalp leads after it had spread to the parietal lobe.
Despite a comprehensive workup, the etiology of our patient's seizures remains unknown. MRI revealed no focal lesions. Further evaluation with a single photon emission computed tomographic scan or cerebral angiogram could not be performed as the patient's liver transplant began to fail shortly after cessation of her seizures.
Seizures are a known complication of liver transplantation. They usually occur in a bimodal distribution at 1 week and 5-16 weeks after surgery and are usually generalized (8). Infection, stroke, central pontine myelinolysis, and drug toxicity are among the different etiologies for posttransplant seizures(9). Of the medications that can induce seizures in transplant patients, calcineurin inhibitors, like tacrolimus, are a potential cause (10,11). In a retrospective study of tacrolimus-related seizures by Sevmis et al (11), 9% of liver transplant patients receiving tacrolimus developed seizures within the first 2 weeks of surgery, despite therapeutic levels. All these patients had generalized tonic-clonic seizures, and about 40% of them had evidence of posterior reversible encephalopathy syndrome on MRI.
This case demonstrates many of the classic findings of parietal and occipital seizures, including eyelid fluttering, gaze preference, and elementary and complex visual hallucinations. In addition, this case illustrates that ictal homonymous visual field defects may occur, and if recognized and treated promptly, these field defects may resolve.
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