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Neurology

Mega Cisterna Magna (Archived)

The cisterna magna is a cerebrospinal fluid (CSF) filled space located in the posterior fossa dorsal to the medulla and caudal to the cerebellum. Mega cisterna magna refers to a cystic posterior fossa malformation characterized by an enlarged cisterna magna, absence of hydrocephalus, and an intact cerebellar vermis. The concept of mega cisterna magna was first introduced in the 1960s by Gonsette; its size was initially described on ventriculography as above 15 mm in anteroposterior length, 5 mm

v1 · Reviewed Nov 8, 2026 by Automated Clinical Reviewer (Strict Verbatim v1)
  • if hydrocephalus is present, the diagnosis of mega cisterna magna should be questioned.
  • Physical examination during the perinatal period should include a search for additional neurologic and systemic malformations, including headache, nausea/vomiting, paresthesias, weakness, ataxia, etc.
  • Mega cisterna magna may now be evaluated with ultrasonography in the fetus or newborn before fontanelle closure.
  • Following fontanelle closure, the mega cisterna magna is best evaluated by computed tomography (CT) and magnetic resonance imaging (MRI) of the brain, with and without contrast, as the gold standard to rule out similar-appearing pathologies.
  • It is critical to exclude ventriculomegaly and cerebellar hypoplasia before diagnosing mega cisterna magna.
  • Radiographically, the mega cisterna magna appears as a prominent retrocerebellar CSF-filled space measuring greater than 10 mm on mid-sagittal images with a normal cerebellar vermis and ventricular caliber.
  • Additionally, there should be no associated enhancement.
  • Clinically, a neuropsychiatric evaluation could be considered if there is any clinical concern.
  • No specific treatment is necessary for patients with incidentally discovered mega cisterna magna.
  • Medications may treat associated signs/symptoms that may or may not be directly related to the mega cisterna magna, including headache, seizure, or psychiatric illness.
  • For mega cisterna magna, there is no specific treatment or surgical intervention indicated.
  • There is a limited role for surgical intervention, which may include CSF diversion for the treatment of hydrocephalus.
  • Other surgical interventions include suboccipital craniectomy, with the surgical exploration of 2 patients in an early study without relief of patient symptoms.
  • There is no clear established follow-up timeline for patients with mega cisterna magna.
  • It is probably reasonable to follow patients into adolescence and early adulthood, as manifestations, if present, may not initially present in early childhood.
  • There are no clear follow-up guidelines for adults with incidentally discovered mega cisterna magna.
  • It is likely reasonable in an asymptomatic adult with an incidentally discovered cisterna magna on a high-resolution image, such as an MRI of the brain, to follow up on an as-needed basis with repeat imaging obtained if new symptoms were to develop.
  • In a recent meta-analysis of 144 fetuses with mega cisterna magna, the rates of additional central nervous system (CNS) and extra-CNS anomalies were 12.6% and 16.6%, respectively, without any identifiable chromosomal abnormality.
  • There have been reported psychiatric associations between mega cisterna magna, including mania, bipolar disorder, schizophrenia, and catatonia.
  • However, patients with isolated mega cisterna magna in a small case series have been found to score lower than controls on specific parameters, including memory, executive functioning, and verbal fluency.
  • In an older study identifying 14 cases of isolated mega cisterna magna out of 1,260 reviewed CT scans, long-standing neurologic dysfunction was reported in 57% of patients (8/14).
  • review
    Mega Cisterna Magna (Archived). StatPearls [Internet] — Luke J. Weisbrod, William Thorell — StatPearls Publishing, 2023

Decision support only. Verify against local protocols and current labeling. Source: www.ncbi.nlm.nih.gov