Colloid cyst is a rare and benign intracranial lesion containing mucoid fluid, thought to arise from embryological remnants in the roof of the third ventricle.^1–3 The usual age at diagnosis occurs within the second to fifth decades of life, with predilection in men. It is slow growing, eventually blocking the foramen of Monro and causing obstructive hydrochephalus.^1,2 Colloid cysts may be asymptomatic, but symptoms can arise from raised intracranial pressure (ICP), secondary to obstructive hydrocephalus.^1,2 Sudden death due to untreated hydrocephalus and raised ICP is well recognised in patients with colloid cyst.^1,3

CASE REPORT

A 24 year old South Asian woman, who was 16 weeks pregnant, presented to the accident and emergency (A&E) department, with a 2 day history of frontal headache and nausea associated with an episode of vomiting. She was neurologically intact, with no signs of meningism or raised intracranial pressure. The baseline heart rate was 72 beats/min and systemic blood pressure was 100/65 mmHg. Her headaches improved with 1 g of paracetamol, following which she discharged herself from hospital.

At home, she continued to complain of intermittent headaches and 2 days later, she was found unconcious by her family, who were unable to rouse her. The ambulance service found her in a state of cardiorespiratory arrest (electromechanical dissociation), with bilaterally dilated and unreactive pupils. After cardiopulmonary resuscitation, cardiac output was regained, but she remained deeply unconscious, with no change in the pupillary state.

Family history revealed the sudden death of her mother and a maternal aunt at a young age, the cause of death being unclear in both cases. Of five siblings, one sister had died suddenly at the age of 21 years from a third ventricular colloid cyst, confirmed at postmortem examination.

An emergency computed tomography (CT) scan confirmed the presence of a hypodense third ventricular colloid cyst with acute hydrocephalus affecting the lateral ventricles (fig 1). Bilateral external ventricular drains were inserted as an emergency, releasing clear cerebrospinal fluid under raised pressure (30 ml of water). Postoperatively, there was no change in her neurological status and the pupils remained unchanged. She was declared dead after fulfilling brainstem criteria, 48 hours later. The family declined postmortem examination and any screening of the remaining family members.

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Figure 1

 Pre-operative unenhanced CT scan of brain shows bilateral enlargement of the lateral ventricles (a) and a hypodense lesion (arrow) in the third ventricle (b).

DISCUSSION

Of patients presenting to the emergency department, 1.7% describe headaches as the main symptom, and of these patients, <15% have a secondary cause for headache.⁴ Colloid cyst of the third ventricle is a rare benign intracranial lesion, accounting for <0.5% of brain tumours.^1–3 Thus, it is an unusual cause of headache in the A&E setting.

Colloid cysts can be entirely asymptomatic, with no clinical signs, and be discovered only incidentally.^1–3 In symptomatic patients, headache (68%), gait disturbance (47%), and short term memory disturbances (37%) are the most common symptoms, with papillo-oedema (47%) and ataxia (32%) the most common signs.¹ Symptoms may be intermittent and are thought to be related to the movement of the colloid cyst on its pedicle from the roof of the third ventricle, causing episodic obstruction of the foramen of Monro, and intermittent intracranial hypertension. As in our case, sudden loss of consciousness or death from acute obstructive hydrocephalus and the resultant cerebellar herniation is a real risk.^1,3 In the pre-CT era, changes in cerebrospinal fluid dynamics from procedures such as lumbar punctures may have contributed to the rate of sudden death reported in these patients.^1,2,5

In the present case, the eventual diagnosis of obstructive hydrocephalus secondary to a hypodense third ventricular colloid cyst was made on CT imaging. Most colloid cysts are hyperdense on CT scans, although isodense and hypodense colloid cysts have also been noted.^2,6–8 Colloid cysts rarely calcify and may show enhancement with contrast. Magnetic resonance (MR) imaging is a better imaging technique for these lesions, but occasionally, colloid cysts may be isosignal intensity on MR, and CT imaging may be more useful.⁸

The optimal treatment of colloid cysts is controversial. Early detection and total excision of the colloid cyst carries an excellent prognosis.^2,3,6,9 As in our patient, the acute hydrochephalus associated with the colloid cyst may require emergency drainage. Definitive treatment of colloid cysts is by surgical excision, through an open craniotomy (transcallosal or transcortical) or by endoscopy.^2,3,6,9 Stereotactic aspiration of the cyst contents has also been described, although there is a higher incidence of recurrence.^2,6,9 The management of asymptomatic cases is influenced by the lesion size (usually surgical intervention when >10 mm in diameter), the presence of hydrocephalus, and the patient’s age, preference, and associated medical conditions.^3,9

Familial cases of colloid cyst are extremely rare.^5,10–13 The age range is from 14–73 years and there is a slight female predominance. Although our patient was pregnant at the time of presentation, this association has not been previously recognised.^5,10–13 Most patients identified with familial colloid cysts have been treated surgically, even when asymptomatic, although a few patients have been successfully managed conservatively with regular clinical and radiological follow up.^5,10–13

Genetic factors may play a role in the familial occurrence of this lesion, although specific chromosomal abnormalities are yet to be isolated.^10,11 The inheritance pattern is probably autosomal dominant, and there may be an association with other congenital defects.^10–13 Screening is of value for families in which two or more members are affected.^10–13

The present case emphasises the need for a low threshold for admission and investigation of headaches, in patients with a family history of colloid cysts; the consequence of missing this benign condition could be devastating.