Colloid cyst: an unusual cause of seizure.

A 46-year-old female presented to the emergency department after two episodes of new-onset generalized tonic–clonic seizures. She was lethargic and mildly confused with a blood pressure of 143/84 mm Hg, pulse of 69/min, oral temp of 36.6°C (97.9°F), respiratory rate of 14/min, and saturation of 93% on room air. She complained of mild headaches but had no nausea and vomiting. There were no focal neurological deficits on exam. Computed tomography (CT) scan of head showed a 5×5 mm well-circumscribed focal hyperdensity in the region of the foramen of Monro on the roof of the third ventricle, most consistent with a colloid cyst without any mass effect (Fig. 1). Metabolic and infectious etiologies were ruled out and the EEG was negative. Further imaging with contrast-enhanced magnetic resonance imaging (MRI) of the brain confirmed the CT findings. She was given intravenous (IV) lorazepam 1 mg and started on 500 mg of oral levetiracetam daily. The confusion improved gradually over the next day. Neurosurgery and neurology were consulted. Levetiracetam was continued and elective surgical removal was offered to the patient. On subsequent follow up with neurosurgery and neurology, she complains of on and off headache and is being maintained on levetiracetam. However, she has not decided on surgery till the time of writing.

Fig. 1

Computed tomography scan of the head showing a well-circumscribed 5×5 mm round hyperdensity in the region of the foramen of Monro.

Discussion

Colloid cysts of the third ventricle are fairly uncommon benign brain masses, representing about 1% of all intracranial neoplasms (1). Clinical presentations vary from asymptomatic to a wide array of features secondary to the rate and size of hydrocephalus development when the CSF flow is obstructed. Most common presentations are headache (intermittent, short-lasting, positional) (2), nausea, and vomiting (3). The positional characteristics are due to mobility of the cyst that blocks foramen of Monro by ball valve mechanism only in certain a position such as standing (relieved when lying down versus the pain of other intracranial space occupying lesion) (4) and subsequent development of acute intracranial hypertension. Vertigo, memory deficit, diplopia and behavioral disturbances are other presentations. Sudden death can happen secondary to acute hydrocephalus or hypothalamic dysfunction leading to cardiovascular failure (3). Seizures and focal neurological deficits as presenting symptoms are rare (1 out of 19 cases in one of the case series) (5). Imaging has a key role in the evaluation of new onset of seizures to detect underlying masses and malformations as potential cause(s) often in combination. Colloid cysts, although a rare cause of seizures, have a characteristic appearance on CT and MRI. It is important to differentiate them from other mass lesions by their typically round, well-circumscribed, hyperdense appearance in relation to gray matter with peripheral contrast enhancement corresponding to capsule cyst and located almost always in the third ventricle posterior to the foramen of Monro on a CT scan (6), as it is surgically curable by various approaches, including stereotactic, microendoscopic, and microsurgical resection. This may prevent recurrence and avoidance of lifelong anti-seizure medications.