Case report: epileptic nystagmus in nonconvulsive status epilepticus

A 19-year-old woman had herpes encephalitis resulting in nonconvulsive status epilepticus (NCSE) and epileptic nystagmus (EN), a condition for which there are few reports. EN is characterized by rhythmic ocular oscillations secondary to seizure activity. The fast component of nystagmus is known to be contralateral to the epileptogenic focus. The authors conclude that when evaluating an obtunded/comatose patient with unexplained altered mental status or coma with or without abnormal motor activity, NCSE should be considered. However, the diagnosis requires a high index of suspicion and must be verified by EEG.

The patient was admitted to the hospital with a headache, fever and altered mental status. She was subsequently diagnosed with herpes encephalitis after complaining of a right homonymous hemianopia and deteriorating into a stuporous state. Cerebrospinal fluid examination revealed a white blood cell count of 19/mm3 and herpes simplex virus IgG titer of 2.6 IU/mL. Brain MRI demonstrated high signal intensities involving portions of the left temporal and occipital lobes.

She was treated with intravenous acyclovir but continued to deteriorate. She had no response to painful stimuli and developed spontaneous conjugate right-beating nystagmus with tonic deviation toward the right side. The slow component of nystagmus did not cross the midline. Her head paroxysmally deviated to the right along with her eyes and showed episodic bilateral eyelid elevation. EEG revealed spiky rhythmic alpha activity in the left posterior region of the head, which evolved into repetitive sharp waves.

The authors believed the patient had NCSE with EN and administered intravenous phenytoin and lorazepam. This led to almost immediate suppression of ictal activity and disappearance of nystagmus, with progressive improvement in cognitive function.

The authors say the patient’s EN was probably due to epileptic discharges in the cortical saccade regions of the frontal eye field (frontal precentral sulcus), the parietal eye field (anterior angular sulcus) or posterior parietal cortex (inferior parietal lobule). They say this is supported by the MRI findings, the tonic deviation of the eyes to the right, the slow phase of the nystagmus that did not cross the midline and the onset of ictal discharges localized over the parieto-occipital electrodes.