====== Disconnection procedure ======

[[Functional hemispherectomy]]/[[hemispherotomy]] is a [[disconnection procedure]] for [[severe medically refractory epilepsy]] where the seizure foci diffusely localize to one [[hemisphere]]. It is an improvement on anatomical [[hemispherectomy]] and was first performed by Rasmussen in [[1974]]. Less invasive surgical approaches and refinements have been made to improve seizure freedom and minimize surgical [[morbidity]] and [[complication]]s. 
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Although the effectiveness of [[hemispherectomy]] was established, the high incidence of [[hydrocephalus]] and delayed mortality from superficial cerebral [[hemosiderosis]] in up to one-third of patients led to a rapid decline in the procedure
((Oppenheimer DR, Griffith HB: Persistent intracranial bleeding as a complication of hemispherectomy. J Neurol Neurosurg Psychiatry 29:229–240, 1966))
((Wilson PJ: Cerebral hemispherectomy for infantile hemiplegia. A report of 50 cases. Brain 93:147–180, 1970)).

In the 1970s, Rasmussen recognized that the [[extent of resection]] and the residual surgical cavity were contributing factors to superficial [[cerebral hemosiderosis]]. Preservation of the frontal and occipital lobes and disconnecting them from the rest of the brain resulted in a “functional complete but anatomical subtotal hemispherectomy,” giving rise to the functional hemispherectomy, which protected against superficial cerebral hemosiderosis and delayed hydrocephalus, and to a resurgence for the [[disconnection procedure]]
((Rasmussen T: Hemispherectomy for seizures revisited. Can J
Neurol Sci 10:71–78, 1983)).
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Key anatomical structures that are disconnected include the 1) [[internal capsule]] and [[corona radiata]], 2) [[mesial temporal]] structures, 3) [[insula]], 4) [[corpus callosum]], 5) [[parietooccipital connection]], and 6) frontobasal connection. A stepwise approach is indicated to ensure adequate [[disconnection]] and prevent seizure persistence or recurrence. In young pediatric patients, careful patient selection and modern surgical techniques have resulted in > 80% seizure freedom and very good functional outcome. 
Young et al. summarized the history of [[hemispherectomy]] and its development and present a graphical guide for this anatomically challenging procedure. The use of the [[osteoplastic]] flap to improve outcome and the management of [[hydrocephalus]] are discussed
((Young CC, Williams JR, Feroze AH, McGrath M, Ravanpay AC, Ellenbogen RG,
Ojemann JG, Hauptman JS. Pediatric functional hemispherectomy: operative
techniques and complication avoidance. Neurosurg Focus. 2020 Apr 1;48(4):E9. doi:
10.3171/2020.1.FOCUS19889. PubMed PMID: 32234987.
)).