Its natural history is still quite unknown in terms of potential origin and course.
They usually occur in patients with bleeding disorders and are associated with trauma in 83% of cases 2).
Other causes include history of birth trauma, forceps delivery, child abuse with shaking, hemodialysis, anticoagulation and aneurysmal bleeding 3).
Fruin et al. 4) suggested that an occipital blow in the sagittal plane lead to an interhemispheric ASDH because of the anatomic orientation of the veins in the interhemispheric fissure, which tend to course antero-medially from the cortex to the midline sinuses. Before the CT era, it was difficult to detect an interhemispheric ASDH. Though removal of the blood has proved to be an option in the management of these patients, there is danger due to the close proximity of the superior sagittal sinus and bridging veins. Some of these hematomas migrate superiorly (to a more favorable position) with time, as they liquefy. It is also conceivable that if a patient with an interhemispheric ASDH is relatively asymptomatic, initial conservative management might be followed by migration of the clot to a position over the convexity where removal is considerably less dangerous. Thus there is no consensus on the ideal management of these rare hematomas, conservative treatment may be followed in those who are neurologically stable or have concurrent risk factors, while surgical treatment should be reserved for those who have pronounced symptoms or neurological deficits 5).
The hyperdense hematoma can best be visualized on the coronal and sagittal views. This is in contrast with typical subdural hematomas, which can be best appreciated on the axial views. Thus, it is important to image all three main views of the brain looking out for interhemispheric hematoma 6).
Ishikawa E, Sugimoto K, Yanaka K, Ayuzawa S, Iguchi M, Moritake T, Kobayashi E, Nose T. Interhemispheric subdural hematoma caused by a ruptured internal carotid artery aneurysm: case report. Surg Neurol. 2000;54:82–6. doi: 10.1016/S0090-3019(00)00262-7.
Twenty adult cadaveric brains and four adult cadaveric heads were studied, using a magnification ranging from 3 times to 40 times, after perfusion of the arteries and veins with colored latex.
The choroidal fissure is a natural cleft between the thalamus and the fornix, and it is identified by following the choroid plexus in the lateral ventricle. The choroid plexus in the body of the lateral ventricle originates from the tela choroidea of the roof of the third ventricle and is apparently attached to the fornix by the taenia fornicis and to the thalamus by the taenia choroidea. The taenia is actually the ependyma that covers the internal wall of the ventricular cavity and the choroid plexus.
An understanding of the choroidal fissure is fundamental for use of the transchoroidal approach. Unlike transforaminal, subchoroidal, subforniceal, and interforniceal approaches to the third ventricle, which sacrifice some neural or vascular structures, the transchoroidal approach follows a natural route, and certainly it is one of the options to be considered when entry into the third ventricle is required 2).
Ito et al demonstrate an interhemispheric transchoroidal approach for third ventricular teratoma resection. Interhemispheric dissection exposed the corpus callosum at a length of about 2 cm. A callosotomy was made to enter into the right lateral ventricle. After septal vein ligation, dissection was made of the space between the right fornix and right internal cerebral vein (ICV); thus bilateral fornix and left ICV would be retracted to the left; right choroid plexus, right ICV to the right. By this transchoroidal approach, the foramen of Monro was extended posteriorly, providing enough of a surgical corridor to resect a posteriorly located third ventricular tumor. The video can be found here: https://youtu.be/gIzPiH3zx_o3).
Interhemispheric transcallosal route for resection of anterior third ventricular lesions
Peker HO, Aydin I, Dinc C, Baskaya MK. Microsurgical Resection of Thalamic Astrocytomas Via Anterior Interhemispheric Transcallosal Transchoroidal Approach: Demonstrating of Technique: 3-Dimensional Operative Video. Oper Neurosurg (Hagerstown). 2018 May 1;14(5):595. doi: 10.1093/ons/opx196. PubMed PMID: 28961966.
Wen HT, Rhoton AL Jr, de Oliveira E. Transchoroidal approach to the third ventricle: an anatomic study of the choroidal fissure and its clinical application. Neurosurgery. 1998 Jun;42(6):1205-17; discussion 1217-9. PubMed PMID: 9632178.
Ito Y, Inoue T, Tamura A, Tsutsumi K. Interhemispheric transchoroidal approach to resect third ventricular teratoma. Neurosurg Focus. 2016 Jan;40 Video Suppl 1:2016.1.FocusVid.15401. doi: 10.3171/2016.1.FocusVid.15401. PubMed PMID: 26722682.