Clinical History
A 29 years old male presented with a intense sudden onset headache.
Imaging Findings
A 29 year old male patient came to the emergency department with a sudden onset of intense holocrania headache exacerbated with Valsava and sudden changes of head position. There was no improvement after analgesia.
Neurological examination was unremarkable aside from pain with cervical flexion.
Unenhanced CT (Figure 1) showed a non communicating hydrocephalus with generalized cerebral oedema. Slight hiperdensity of the basal cisterns and Sylvius cisures was reported.
The patient was admitted for further investigation, including two cerebral digital subtraction angiographies (Figure 2), which were normal.
He improved substantially and was released 14 days after admission.
Three months later, he was again admitted to the emergency department with a violent bifrontal headache with periods of drowsiness alternating with agitation.
Unenhanced CT (Figure 3) showed a non communicating hydrocephalus with generalized cerebral oedema.
Lumbar puncture showed an opening pressure of 28cm3 H2O, normal cell count and chemistry.
The patient then underwent MRI (Figure 4) that showed a small cystic lesion next to the Monro's foramen, hyperintense on T2, T2* and FLAIR and iso-intense on T1 weighted images, findings consistent with a colloid cyst of the third ventricle.
A ventriculoperitoneal shunting was performed resolving the hydrocephalus.
The patient was proposed with surgical treatment and preferred a non invasive approach.
Six months later, an MRI study was performed (Figure 5) showing a signal change of the colloid cyst on different sequences, namely, hyperintensity on T1 images and hypo-intensity on the T2 images. These changes were highly suggestive of spontaneous bleeding within the cyst. There was no hydrocephalus.
Discussion
Colloid cysts of the third ventricle are unilocular mucin containing cysts that account for about 0.5-1% of all intra-cranial tumours and 15-20% of intraventricular masses. The annual incidence is approximately 3 per one million population.
They are more frequent in the 3rd and 4th decade of life, but cases on both extremes of age have been reported.
Typically colloid cysts are located on the third ventricle, attached to the ventral aspect of its roof, and wedged into the foramen of Monro but in less than 1% of cases they can be located elsewhere in the neuroaxis.
Headache is the most frequent symptom (68-100% of patients); it is usually characterized as brief and as being initiated, exacerbated or relieved by a change in position. Other described symptoms are vomiting, visual disturbances, episodes of loss of consciousness, sleepiness, vertigo and progressive dementia.
Because symptoms are unspecific and intermittent with long asymptomatic intervals, diagnosis can be difficult.
Neurological exam can be totally normal, but usually shows signs of increased intracranial pressure like bilateral papilledema and decreased visual acuity.
While histological benign, this lesion can lead to sudden death; the proposed mechanism is an acute obstructive hydrocephalus with overtake of compensatory mechanisms, resulting in collapse of the superior sagital sinus, venous stasis and brain swelling leading to acute neurological deterioration and sudden death.
Diagnosis is usually made based on neuroimaging, and both CT and MRI can be used to this effect. On CT scan, the density of colloid cysts is related to the hydration state; they are hyperdense in about 2/3 of cases and iso/hypodense in 1/3; the latter can be difficult to see, especially when they are small.
Colloid cysts have a variable appearance on MRI imaging. On T1 weighted images, signal correlates with cholesterol concentration; they are hyperintense in 2/3 of cases and isointense in 1/3 of cases; on T2 weighted images, signal usually reflects water content; most cysts are isointense to brain. Haemorrhage inside the cyst can also contribute to the T1 and T2 signal.
Haemorrhage is a very rare complication of the colloid cyst. Spontaneous bleeding within the cyst can lead to the increase of the cyst size; this has been proposed as one of the mechanisms that contribute to the onset and exacerbation of symptoms, and one of the causes of sudden death.
In our case, the changes of the signal of the colloid cyst between the first and second MRI raise the possibility of a small spontaneous bleeding of the colloid cyst.
The finding of a non communicating hydrocephalus confined to the lateral ventricles should prompt the neuroradiologist to exclude the presence of a colloid cyst; since small hypodense cysts may not be seen on CT, MRI is mandatory.
Differential Diagnosis List
Colloid cyst of the third ventricle
Final Diagnosis
Colloid cyst of the third ventricle
