====== Interhemispheric Subdural Hematoma Epidemiology ======

Interhemispheric [[subdural hematoma]] (ISH) had been considered extremely rare until identification with imaging studies. 

IHSDHs are often referred to as rare entities. Results show they are common
((Léveillé E, Schur S, AlAzri A, Couturier C, Maleki M, Marcoux J. Clinical Characterization of Traumatic Acute Interhemispheric Subdural Hematoma. Can J Neurol Sci. 2020 Jul;47(4):504-510. doi: 10.1017/cjn.2020.44. Epub 2020 Mar 3. PMID: 32122420.)).

Interhemispheric subdural hematoma (IHSDH) is an uncommon type of subdural hematoma (SDH) because of their unusual location
((Shankar A, Joseph M, Chandy MJ. Interhemispheric subdural hematoma: an uncommon sequel of trauma. Neurol India. 2003 Mar;51(1):63-4. PMID: 12865519.))
((Sogut O, Yigit M, Turkdogan KA, Yigit E, Gulen B, Sonmez E, Kaplan O, Toprak H. Interhemispheric Acute Subdural Hematoma: A Distinct Entity of Subdural Hematoma. J Clin Med Res. 2016 Feb;8(2):178-9. doi: 10.14740/jocmr2427w. Epub 2015 Dec 28. PMID: 26767089; PMCID: PMC4701076.)).
It accounts for approximately 6% of all traumatic SDH, or 0.8% of all hospitalized patients after head trauma
((Takeda N, Kurihara E, Matsuoka H, Kose S, Tamaki N, Matsumoto S. [Three cases of acute interhemispheric subdural hematoma]. No Shinkei Geka. 1988 Jan;16(1):87-92. Japanese. PMID: 3283592.))
((Takeuchi S, Takasato Y, Masaoka H, Hayakawa T, Yatsushige H, Sugawara T. Traumatic interhemispheric subdural haematoma: Study of 35 cases. J Clin Neurosci. 2010 Dec;17(12):1527-9. doi: 10.1016/j.jocn.2010.03.055. PMID: 20817537.)).

Till 1995, less than 70 cases were reported in the literature
((Bartels RH, Verhagen WI, Prick MJ, Dalman JE. Interhemispheric subdural hematoma in adults: case reports and a review of the literature. Neurosurgery. 1995 Jun;36(6):1210-4. doi: 10.1227/00006123-199506000-00026. PMID: 7644007.)).

Only about 100 cases have been reported till [[1997]]
((Sadrolhefazi A, Bloomfield SM. Interhemispheric and bilateral chronic subdural hematoma. Neurosurg Clin N Am. 2000;11:455–63))
((Houtteville JP, Toumi K, Theron J, Derlon JM, Benazza A, Hubert P. Interhemispheric subdural haematomas: seven cases and review of the literature. Br J Neurosurg. 1988;2:357–67. doi: 10.3109/02688698809001007.))
((Rapanà A, Lamaida E, Pizza V, Lepore P, Caputi F, Graziussi G. Inter-hemispheric scissure, a rare location for a traumatic subdural hematoma, case report and review of the literature. Clin Neurol Neurosurg. 1997;99:124–9. doi: 10.1016/S0303-8467(96)00585-9.)).

Interhemispheric ASDHs are usually unilateral but bilateral hematomas have also been reported. Interhemispheric ASDH usually occurs posteriorly in the majority of cases.