Abstracts

Rationale: Episodic encephalopathy may mimic seizures. There are few reported causes of recurrent stereotyped encephalopathy. We present a case of unusual electroclinical episodes with electroencephalogram (EEG) features of encephalopathy rather than epilepsy. Diagnostic evaluation revealed the cause to be carcinomatous meningitis associated with increased intracranial pressure (ICP); this unusual presentation merits reporting.Methods: A 56 year old woman presented with confusional episodes and falls. At age 37, she underwent lumpectomy and radiotherapy for breast carcinoma. At age 47, bilateral breast cancer recurrence was treated with bilateral mastectomy, radiotherapy, and chemotherapy. She was in remission for 8 years when she developed episodes of headaches, confusion, trembling, and weakness leading to frequent falls. Extensive workup, including repeated brain MRIs revealed no diagnosis. Symptoms worsened over three months. She was then referred for video-EEG monitoring at the UCSD Epilepsy Center.Results: Interictally, she was neurologically normal and her EEG showed 8-9Hz posterior dominant rhythm with nonspecific diffuse theta. We recorded multiple daily episodes lasting 10-20 minutes; she became dazed, bradyphrenic, and weak with oral and left lower limb automatisms, severe headache and diplopia. The EEG showed generalized, irregular, 6-7 Hz theta activity, admixed with intermittent, high amplitude, polymorphic and occasionally rhythmic 2-3 Hz delta potentials, maximal in the bifrontal head regions and resembling frontal intermittent rhythmic delta activity (FIRDA) (Figure 1). EEG changes persisted for 10-20 minutes followed by a gradual return to the waking background rhythm. A repeat MRI brain revealed new hydrocephalus with leptomeningeal enhancement (Figure 2). Subsequently, a large volume lumbar puncture (LP) was done during one of the patient s episodes. It revealed an opening pressure greater than 50 cm H2O and a closing pressure of 5 cm H2O. The cerebrospinal fluid (CSF) showed normal WBC and RBC, elevated protein of 220 mg/dL and decreased glucose of 44 mg/dL. CSF cytology showed malignant cells consistent with breast carcinoma. After the large volume LP, she had no further events for the subsequent 2-3 days. She was transferred to the neuro-oncology service, and a ventriculoperitoneal (VP) shunt with Ommaya reservoir was placed. Episodes improved thereafter.Conclusions: The patient s findings were consistent with metastatic breast carcinoma involving the leptomeninges, with elevated ICP. The episodic nature of her encephalopathy, accompanied by characteristic changes on EEG, is best explained by episodic intracranial plateau waves. These symptoms were the first indication that the malignancy had recurred intracranially when her MRI brain was repeatedly normal. Dramatic improvement after a large volume lumbar puncture and VP shunt is further evidence for increased ICP as the cause of her encephalopathy. In evaluating seizure-like episodes, it is important to recognize transient ICP elevation as an unusual cause of stereotyped episodic encephalopathies.