Quadrigeminal Plate Arachnoid Cyst

Compared to supratentorial arachnoid cysts, infratentorial arachnoid cysts are more frequently symptomatic. Typical locations are:

• Retrocerebellar: Common location.
• Cerebellopontine angle: Common location.
• Quadrigeminal plate cistern: Third most common infratentorial location. Located between the collicular plates and the incisural notch of the tentorium cerebelli.
• Along the lateral aspect of the cerebellum
• Along the clivus

Quadrigeminal plate cistern arachnoid cysts are also known as paracollicular arachnoid cysts, tentorial notch arachnoid cysts, arachnoid cysts of cisterna ambiens, paramesencephalic arachnoid cysts, and parapineal arachnoid cysts.

Symptoms may be related to normal pressure hydrocephalus, Parinaud syndrome, visual disturbances, nystagmus, hearing deficits, hemiparesis, paraparesis, generalized spasticity, clonus, diplopia caused by trochlear nerve compression, lateral rectus palsy caused by intracranial hypertension, and precocious puberty.

It's important to look for mass effect on adjacent structures, including the sylvian aqueduct. An important differential consideration is a cyst of the tectal plate, which is intraparenchymal. As such, a tectal plate cyst is covered by a rim of brain tissue whereas a quadrigeminal cistern cyst is not.

The standard differential is

• Epidermoid cyst: don't suppress on FLAIR and show restricted diffusion.
• Chronic subdural hematoma: Not identical to cerebrospinal fluid signal.
• Subdural hygroma: Often bilateral
• Other nonneoplastic cyst: porencephalic cyst, neurenteric cyst, neuroglial cyst

The image is that of a middle-aged man who presented with sudden onset dizziness. There is cystic lesion in the quadrigeminal plate cistern that follows cerebrospinal fluid signal without diffusion restriction or abnormal enhancement. The signal is completely suppressed on FLAIR. There is no hydrocephalus and the sylvian aqueduct is patent. There is, however, mass effect on the cerebellum.

References

• Kumar V, Peng EW, Fitzpatrick MO, Whittle IR. Tectal plate cyst in adults. Acta Neurochir (Wien). 2006 Jul;148(7):805-8.
• Little JR, Gomez MR, MacCarty CS. Infratentorial arachnoid cysts. J Neurosurg. 1973 Sep;39(3):380-6.
• Topsakal C, Kaplan M, Erol F, Cetin H, Ozercan I. Unusual arachnoid cyst of the quadrigeminal cistern in an adult presenting with apneic spells and normal pressure hydrocephalus--case report. Neurol Med Chir (Tokyo). 2002 Jan;42(1):44-50.