Type 1 Chiari Malformation (T1CM) refers to a congenital herniation of the cerebellar tonsils though the foramen magnum of ≥5 mm (Pickard et al., 2012). Total prevalence in normal adults is almost 1%, yet only 0.01–0.04% of the population are symptomatic (Tubbs, 2013). The ectopic tonsils may cause obstruction of cerebrospinal fluid (CSF) flow through the subarachnoid space at the craniocervial junction (Pickard et al., 2012). Patients may be asymptomatic, or display varied symptoms due to brainstem compression, cerebellar displacement, traction on cranial nerves or interference with CSF flow. Transiently elevated intracranial pressure (ICP) due to trapped cerebrospinal fluid causes the most common symptom, headaches, in 81% of patients (Fischbein et al., 2015). 10% of patients have associated hydrocephalus (Tubbs, 2013), and an unknown percentage have idiopathic intracranial hypertension.
- foramen magnum
- cerebellar tonsils
- congenital herniation
- Type 1 Chiari Malformation (T1CM)
- Electroconvulsive therapy