What is the definition of arachnoid cysts?
Arachnoid cysts are extra-axial, benign cystic lesions, of unknown etiology, probably formed due to a congenital splitting of the arachnoid layer.
Where are the locations that arachnoid cysts may occur?
Arachnoid cysts may develop at anterior cranial fossa, middle cranial fossa, cerebral convexity, interhemispheric, cerebellopontine angle cistern (CPA), supracerebellar, lateral cerebellar, retrocerebellar, ambient cistern, quadrigeminal cistern, retrocerebellar, cisterna magna, brainstem (perimedullary or prepontine), and spinal canal.
What is the most common arachnoid cyst location in the adult population?
The most frequent location of arachnoid cysts in the adult population is the middle cranial fossa.
What are the symptoms and signs of arachnoid cysts?
The majority of patients with arachnoid cyst are asymptomatic. Symptomatology will depend on the size and location of the cyst and whether there is a resultant mass effect. Symptoms and signs may include headaches, hydrocephalus, nausea/vomiting, vertigo, seizure, ataxia, dizziness, visual changes, hearing loss, speech abnormalities, mental status changes, cervical myelopathy. The local mass effect may contribute to focal neurological deficits, and can also promote cortical thinning of the bone. These lesions can also rupture, causing hygromas or hemorrhage.
How is the neuroimaging characteristics of arachnoid cysts?
They are isoattenuation to CSF on CT, and isointense to CSF on all MRI sequences. They do not enhance, and they do not exhibit diffusion restriction on MRI.
When is the treatment of arachnoid cyst indicated?
The treatment of arachnoid cyst is controversial, and the indication is generally for symptomatic cysts. There are several neurosurgical techniques options: shunting of hydrocephalus, cystoperitoneal shunting, ventricular-cystocysternostomy, complete resection of an arachnoid cyst, microsurgical fenestration via craniotomy, neuroendoscopic fenestration.
Magnetic resonance (MR) imaging with gadolinium shows a small cyst located at the quadrigeminal cistern, following cerebrospinal fluid (CSF) signal in all pulse sequences, homogeneously hypointense on T1 weighted MR and FLAIR images, and hyperintense com T2 weighted MR, without contrast enhancement. The cyst does not restrict on diffusion-weighted images, and it shows facilitated diffusion. It measures 1,6 x 1,6 x 2,0 cm. The cyst is exerting slight compression over the cerebellum. There is no compression on the aqueduct and no hydrocephalus.