A 16-year-old girl presents to the emergency department with an acute-onset severe headache as well as nausea, vomiting, and intermittent diplopia. She feels dizzy while walking and cannot walk independently. She also complains of blurred vision. This is her first physician's visit for the headaches, which have been episodic during the past 2 weeks. The headaches involve her entire head. They are not throbbing and are not associated with an aura or a certain time of the day. The severity increases while coughing or straining. She has photophobia and phonophobia during these episodes. The headaches previously responded to over-the-counter analgesics, but now she has intolerable pain unrelieved by medications. She has no significant medical history, except for minor head trauma while cycling 1 month ago. Her only medication is an oral contraceptive that she has taken for 2 years. She denies any illicit drug use. The family history is positive for atypical migraine headaches; her mother has been treated with medications for this condition for years.
On physical examination, the patient is a normal-appearing teenager, but she is agitated due to her headache. She has a regular heart rate of 65 bpm, her blood pressure is 165/95 mm Hg, and her oral temperature is normal at 98.6°F (37°C). The general physical examination reveals no abnormalities in the head, neck, chest, abdomen, or extremities. A thorough neurologic examination is performed, which reveals decreased visual acuity in each eye to 6/10 (or about 20/30 US Standard). Ophthalmoscopy reveals papilledema, venous engorgement, and a diminished venous pulse. Bilateral sixth cranial nerve palsy is evident. Other neurologic examinations, including sensory and motor examinations, deep tendon reflexes, and cerebellar tests, are all within normal range.
During the initial assessment of the patient in the emergency department, she develops a generalized tonic-clonic seizure, which is immediately controlled with intravenous diazepam. Her blood pressure rises to 175/100 mm Hg, and her heart rate is 60 bpm after the convulsion. A repeat neurologic examination reveals bilateral extensor plantar reflexes and midsized pupils with slight reaction to light. After initiating a loading dose of intravenous phenytoin, an urgent computed tomography (CT) scan of the head is performed.
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Discussion
The new onset of headache with nausea, vomiting, blurred vision, and diplopia were strongly suggestive of increased intracranial pressure in this patient. The presence of bilateral sixth nerve palsy and bilateral papilledema on neurologic examination confirmed this suspicion. Laboratory tests revealed normal electrolytes, renal function, and complete blood count findings. The CT scan of the brain revealed acute lateral ventricular hydrocephalus, with periventricular edema and a hyperdense round mass within the third ventricle causing obstruction of the foramen of Monro. The most likely diagnosis was colloid cyst of the third ventricle.
Colloid cysts of the third ventricle account for 10%-15% of intraventricular tumors. They are the most common masses of the third ventricle found in adults. Controversy exists over whether these cysts can be classified as brain neoplasms. The cysts are considered to be congenital in origin, and there are some reports of familial occurrence of the disease[1,2]; however, no specific gene has been identified. Autosomal dominant inheritance is the proposed mechanism in such cases.[2] Some believe that the cysts originate from the neuroepithelium, but other sources, such as endoderm or ectopic respiratory tissue, have also been hypothesized. The cysts are thin-walled benign masses with a gelatinous content.[3] They are located in the anterior third ventricular area and are connected to the rostral aspect of its roof, projecting inferiorly close to the foramina of Monro. The inner epithelium with simple cuboidal and columnar cells secretes a mucinous content, which accumulates under pressure. Most cysts are asymptomatic and rarely are a cause of headache. In symptomatic cysts, headache is the most common presentation. Persistent or intermittent obstruction of the foramina of Monro is believed to be the cause of headache.[4] Symptomatic cysts typically present in mid-adulthood with headache, signs of increased intracranial pressure, and acute lateral ventricular hydrocephalus, although atypical presentations -- such as hemorrhagic cysts -- have been described during childhood as well.[3] Other symptoms may include altered mental status, nausea and vomiting, seizure, vertigo, and sudden attacks of leg weakness.[2] The latter might be rarely associated with other brain tumors and may be due to stretching of corticospinal nerve fibers to the legs after acute hydrocephalus. The most severe presentation is sudden death. The cause of this rare phenomenon is debatable, but it may be secondary to reflex cardiac effects due to the cyst compressing of the hypothalamus.[2] Acute blockage of cerebrospinal fluid with instant herniation or decompensation in chronic hydrocephalus has also been postulated.[5]
The differential diagnosis of colloid cyst includes a wide range of tumors of the anterior third ventricle. These lesions usually originate outside the third ventricle and deform the ventricle by encroachment of the surrounding parenchyma; however, intraventricular tumors may also be the source of cerebrospinal fluid pathway blockage. Choroid plexus papillomas usually present during the first 2 decades of life. Although 10%-30% are found within the third ventricle, mobile tumors may slip from lateral ventricles into the foramina of Monro and become trapped in the third ventricle, thereby causing hydrocephalus.[6] Neurocytomas are intraventricular tumors that are seen in young adults and may be found in the lateral and third ventricular regions. These tumors are frequently misdiagnosed as oligodendroglioma or ependymoma under light microscopy, and the true incidence of this condition may be more than expected. Intraventricular meningiomas account for 15%-17% of meningiomas in pediatric patients, but only 1.6% of meningiomas in adults.[6] Only 50 reported cases of third ventricle meningioma exist in the literature, and the majority of these lesions are found within lateral ventricles.[6] They commonly present as basal tumors with extension up into the floor of the third ventricle.
As described earlier, most other lesions encroach on the third ventricle from the surrounding parenchyma. The majority of these lesions are glial tumors, including juvenile pilocytic astrocytoma, fibrillary astrocytoma, protoplasmic astrocytoma, subependymal giant cell astrocytoma, glioblastoma multiforme, and ependymoma. Metastatic neoplasms may involve the third ventricle via its roof, floor, lateral wall, or choroid plexus. Metastases from the lungs, colon, kidneys, and breasts are most common. In these cases, the prognosis is poor, and death is often due to progressive systemic disease. Suprasellar germinomas and craniopharyngiomas can invade the floor of the third ventricle from below. Suprasellar extension of pituitary macroadenomas may also involve the third ventricle. Decreased visual acuity or visual field, endocrinopathy, and headache are the main symptoms in these cases.
Other cystic lesions in the anterior third ventricular area include epidermoid cyst, dermoid cyst, and neurocysticercosis. Epidermoid and dermoid cysts are rarely found in the third ventricle, and neurocysticercosis is endemic to Mexico, Eastern Europe, Asia, Central and South America, and Africa. Fenestration into the third ventricle has occurred in 15%-25% of cases with ensuing hydrocephalus.[7] Inflammatory lesions, such as pyogenic abscesses, and granulomatous diseases, such as tuberculosis or fungal infection, may rarely impinge on the third ventricle. Other lesions, such as sarcoidosis and histiocytosis, may involve the third ventricle via its floor and hypothalamus. Finally, vascular lesions, such as cavernous malformations and arteriovenous malformations, should be added to the differential diagnosis of third ventricular mass lesions.
The contents of the colloid cyst determine its appearance on imaging studies. The cyst may be found incidentally on CT scanning or when the patient presents with symptoms and signs of increased intracerebral pressure suggestive of acute obstructive hydrocephalus. It is generally a round homogeneous hyperdense mass within the third ventricle at the level of the foramina of Monro.[5] Acute lateral hydrocephalus with periventricular edema might be seen due to the blockage of the cerebrospinal fluid pathway into the third ventricle. On T2-weighted magnetic resonance imaging (MRI), the cyst might be either hypo- or hyperintense, and fluid-attenuated inversion recovery (FLAIR) shows periventricular edema in the acute stage of hydrocephalus as hyperintensity surrounding the lateral ventricle.
Surgical intervention is indicated after considering certain factors, such as the patient's age, symptoms, and cyst size. Because of the threat of sudden death, surgery is recommended for cysts exceeding 1.5 cm in diameter in young patients, even in asymptomatic cases.[8] Symptomatic patients should always receive treatment.[9] Options for treatment include endoscopic removal of the cyst[10] and open surgery with different approaches, such as transcortical or interhemispheric transcallosal approaches.[4,9]
In this case, MRI revealed a round mass with high signal intensity on T1-weighted imaging, low signal intensity on T2-weighted imaging, and high signal intensity on FLAIR images. The patient was taken to the operating room. Bilateral external ventricular drainage was inserted in the frontal horns of the lateral ventricles. Bilateral drainage was performed because unilateral ventricular drainage may fail to reduce intracranial pressure when a third ventricular mass simultaneously obstructs both foramina of Monro. Unilateral drainage may also result in selective enlargement (or "trapping") of the contralateral lateral ventricle. The tumor was totally resected via a interhemispheric transcallosal approach under a surgical microscope. The macroscopic appearance of the tumor was a creamy soft cyst suggestive of colloid cyst. Histopathology revealed a fibrous wall lined by inner ciliated columnar epithelium and colloid and cell ghosts, confirming the diagnosis. On the first postoperative day, the patient's diplopia and headache resolved. The patient had an uneventful postoperative course and was discharged from the hospital 6 days after surgery. She was on phenobarbital for 6 months, which was tapered and discontinued after a normal EEG. Gradual improvement in visual acuity was observed, and she regained her full vision 5 months later.
(Source: Medscape)
Colloid cyst is most common third ventricle mass
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