====== Interhemispheric parietooccipital approach ======

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see [[Posterior interhemispheric transprecuneus gyrus approach]]


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The interhemispheric parietooccipital [[precuneus]] (para-esplenial) approach, described by Yasargil, provides a short route to the medial wall of the [[trigone]], and at same time avoids injury to the [[optic radiation]]s as well as avoiding disturbance of cortical functions, even in the dominant hemisphere
((Yasargil MG. Parieto-occipital interhemispheric approach. In: Yasargil MG (Ed). Microneurosurgery, vol IVB. New York:Thieme, 1996:56-57.))
((Tokunaga K, Tamiya T, Date I. Transient memory disturbance after removal of an intraventricular meningiomas by a parieto-occipital interhemisferic precuneus approach: case report. Surg Neurol 2006;65:167-169.   )).

The medial surface is retracted and an incision made in the precuneus cortex leaving a short distance (± 2 cm) to the medial wall of the trigone. This route is indicated for small or medium-size meningiomas with medial projection. The disadvantages are wider brain retraction is necessary, the narrow working angle, narrow surgical corridor and difficult access to the choroidal vessels
((Lyngdoh BT, Giri PJ, Behari S, Banerji D, Chhabra DK, Jain VK. Intraventricular meningiomas: a surgical challenge. J Clin Neurosc 2007;14:442-448.))
((D'Angelo VA, Galarza M, Catapano D, Monte V, Bisceglia M, Carosi I. Lateral ventricle tumors: surgical strategies according to tumor origin and development - a series of 72 cases. Neurosurgery 2005;56(Suppl1): S36-S45))
((Wang S, Salma A, Ammirati M. Posterior interhemispheric transfalx transprecuneus approach to the atrium of the lateral ventricle: a cadaveric study. J Neurosurg 2010;103:949-954.)).


Interhemispheric parietooccipital approaches are associated with limited exposure to the more posterior part of the mesial temporal lobe and require significant brain retraction
((de Oliveira JG, Párraga RG, Chaddad-Neto F, Ribas GC, de Oliveira EP: Supracerebellar transtentorial approach resection of the tentorium instead of an opening—to provide broad exposure of the mediobasal temporal lobe: anatomical aspects and surgical applications. Clinical article. J Neurosurg 116:764–772, 2012))
((Türe U, Harput MV, Kaya AH, Baimedi P, Firat Z, Türe H, et al: The paramedian supracerebellar-transtentorial approach to the entire length of the mediobasal temporal region: an anatomical and clinical study. Laboratory investigation. J Neurosurg 116:773–791, 2012)).

The interhemispheric parietooccipital approach allows only limited exposure of the more lateral PMT regions, and the access provided by this approach is restricted to the posterior portion of the mediobasal temporal lobe. Also, retraction of the occipital lobe may result in new-onset visual deficits
((de Oliveira JG, Párraga RG, Chaddad-Neto F, Ribas GC, de Oliveira EP: Supracerebellar transtentorial approach resection of the tentorium instead of an opening—to provide broad exposure of the mediobasal temporal lobe: anatomical aspects and surgical applications. Clinical article. J Neurosurg 116:764–772, 2012)).

====Posterior corpus callosotomy using a parietooccipital interhemispheric approach====
Ito et al. published a surgical [[technique]] for [[posterior callosotomy]] using a [[interhemispheric parietooccipital approach]] with a semi-prone park-bench position as a second surgery. Although this procedure requires an additional skin incision in the parietooccipital region, it makes the 2-stage callosotomy safer and easier to perform because of reduced intracranial adhesion, less bleeding, and an easier approach to the splenium of the [[corpus callosum]]
((Ito H, Morino M, Niimura M, Takamizawa S, Shimizu Y. Posterior callosotomy
using a parietooccipital interhemispheric approach in the semi-prone park-bench
position. J Neurosurg. 2015 Jun 5:1-4. [Epub ahead of print] PubMed PMID:
26047417.)).

===== Indications =====

The approach is mainly used for lesions located in posterior interhemispheric and deep midline structures, including:

==== 1. Tumors ====

Pineal region tumors (e.g., pineocytomas, pineoblastomas, germ cell tumors)

Gliomas of the posterior corpus callosum

Colloid cysts (posterior third ventricle)

Craniopharyngiomas (posterior extension)

Ependymomas of the third ventricle

Meningiomas of the falx, tentorium, or posterior corpus callosum

==== 2. Vascular Lesions ====

Arteriovenous malformations (AVMs) in the splenium, precuneus, or cuneus

Cavernomas in the corpus callosum or posterior interhemispheric region

Aneurysms of the posterior pericallosal or splenial arteries

Dural arteriovenous fistulas (dAVFs) in the posterior falx or tentorium

==== 3. Epilepsy Surgery ====

Resection of epileptogenic foci in the precuneus or posterior cingulate gyrus

Corpus callosotomy (partial or complete) for intractable epilepsy

==== 4. Other Lesions ====

Hydrocephalus due to obstruction of the posterior third ventricle

Callosal disconnection syndromes requiring intervention

Neurocysticercosis or other parasitic cysts in the posterior ventricular system

===== References =====