Tectal Plate Cavernoma: A Rare Brainstem Lesion

A 45-year-old female presented with headache, diplopia and vertigo for two months. On examination, she had positive cerebellar signs and ataxia on tandem walk. Her cranial nerves were intact. Funduscopic evaluation revealed mild papilledema.

Computed tomography revealed a hyperdense lesion in the dorsal midbrain (Figure 1A). Magnetic resonance imaging showed a well-circumscribed lesion located in the right half of the tectal plate appearing predominantly hyperintense on T2 with internal and peripheral hypointensities and fluid-fluid levels giving a popcorn appearance (Figure 1B). On T1, the lesion was isointense, with hyperintense signals in the periphery (Figure 1C). Only minimal internal contrast enhancement was seen on post-gadolinium sequences. Blooming artifact was noted on susceptibility-weighted imaging (Figure 1D).  The findings were consistent with a tectal plate cavernoma causing compression of the cerebral aqueduct and leading to obstructive hydrocephalus. The patient was managed with an endoscopic third ventriculostomy and a ventricular drain insertion for the hydrocephalus. Follow-up imaging after one year did not reveal any change in morphology or size of the cavernoma, and the patient remained neurologically stable.

Cavernomas are uncommon congenital vascular anomalies of the brain characterized by sinusoidal vascular spaces adjacent to each other with no intervening brain parenchyma and occur in any part of the central nervous system. They account for 5-10% of all vascular malformations.

Brainstem cavernomas are rare and account for fewer than 20% of intracerebral cavernomas. Brainstem cavernous malformations have a high incidence of bleeding and re-bleeding and carry a high rate of morbidity. Previous literature has reported re-bleeding rates of up to 30-60% per person per year with fatality of 20% [1, 2]. Locations in the tectal plate represent a small percentage of BCM which have rarely been reported in few sporadic case reports [3-5]. Approximately 57% of the cavernomas occur in pons followed by midbrain (14%), pontomedullary junction (12%), and medulla (5%) [1,2,6]. Multiple cavernomas may also demonstrate a familial inheritance pattern.

Cavernomas have typical imaging features with characteristic popcorn or mulberry appearance on gradient weighted susceptibility imaging MRI is therefore superior to CT in diagnosing brainstem cavernoma. Associated features like perilesional oedema, haemorrhage, and any underlying developmental venous anomaly can be identified on MRI. MRI also helps in differentiating cavernoma from haemorrhage due to other causes like neoplasms, arteriovenous malformations, hypertension or coagulopathy, or metastasis [6].

Management of brainstem cavernous malformations has remained controversial. Microsurgical gross total removal of tectal plate cavernomas has been successfully performed via an occipital transtentorial approach [3,5,6]. Therefore, these authors recommend aggressive surgical extraction of symptomatic brainstem cavernomas if they are easily accessible, if haemorrhage is present, and if the patient's condition permits it. However, some reports of brainstem cavernous malformations have shown dramatic, spontaneous decrease in size of these lesions even in the case of large brainstem cavernoma with haemorrhage [7]. Hence, conservative therapy may be one of the treatment options for the symptomatic lesions. Our patient was also managed conservatively and remained well, with planned active surveillance of the lesion with MRI.