====== Midbrain ======

{{ ::midbrain.jpg?400|}}

The [[midbrain]], [[pons]], and [[medulla oblongata]] differ in their macro-, micro-, and [[functional anatomy]], in both their pathoclisis (preferential vulnerability to pathological processes) and topographic anatomical relations. Differing pathoclisis results in a different incidence and distribution of histotypes in each of the three segments (e.g., low-grade tumors are much more common in the midbrain than in the pons). Histotype and anatomical relations of a target lesion dramatically affect the difficulty of surgery. For example, a [[pons glioma]] poses completely different surgical challenges from those of a [[midbrain glioma]], and a midbrain glioma in turn poses completely different challenges from those of a midbrain [[cavernoma]]. In short, the [[topography]] and [[histopathology]] of the target lesion are crucial criteria for surgical [[decision-making]]. Thus, they are also crucial for identifying homogeneous patients’ subgroups within the larger population of patients harboring brainstem lesions. In light of these considerations, neurosurgical reporting and debate about brainstem surgery should be standardized according to topography and histopathology
((Serra C, Türe H, Fırat Z, Staartjes VE, Yaltırık CK, Ekinci G, Sav A, Türe U. Microsurgical management of midbrain gliomas: surgical results and long-term outcome in a large, single-surgeon, consecutive series. J Neurosurg. 2023 Jul 21:1-12. doi: 10.3171/2023.5.JNS222219. Epub ahead of print. PMID: 37503951.))
----


The top part of the [[brainstem]] that connects the brain to the spinal cord.

The [[midbrain]] or [[mesencephalon]] (from the Greek mesos, middle, and enkephalos, brain is a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation.

The midbrain comprises the [[tectum]] (or corpora quadrigemina), [[tegmentum]], the [[cerebral aqueduct]] (or ventricular mesocoelia or "iter"), and the [[cerebral peduncle]]s, as well as several nuclei and fasciculi. Caudally the midbrain adjoins the [[metencephalon]] (afterbrain) (pons and cerebellum) while rostrally it adjoins the [[diencephalon]] (thalamus, hypothalamus, etc.). The midbrain is located below the cerebral cortex, and above the hindbrain placing it near the center of the brain.

Specifically, the midbrain consists of:

[[Tectum]]

[[Inferior colliculus]]

[[Superior colliculus]]

[[Cerebral peduncle]]

[[Midbrain tegmentum]]

[[Crus cerebri]]

[[Substantia nigra]].
----
[[Dopaminergic neuron]]s of the [[midbrain]] are the main source of [[dopamine]] (DA) in the mammalian central nervous system. 

===== Pathology =====

[[Midbrain hemorrhage]]

[[Midbrain tumor]]s

[[Midbrain cavernous malformation]].

===== Midbrain MRI =====

{{::midbrain_mri.jpeg?200|}}

In a prospective longitudinal design, Hirad et al. demonstrated there are reductions in midbrain white matter integrity due to a single season of collegiate football, and that the amount of reduction in midbrain [[white matter integrity]] is related to the amount of rotational acceleration to which players' brains are exposed. We then replicate the observation of reduced midbrain white matter integrity in a retrospective cohort of individuals with frank concussion, and further show that variance in white matter integrity is correlated with levels of serum-based tau, a marker of blood-brain barrier disruption. These findings mean that noninvasive structural MRI of the midbrain is a succinct index of both clinically silent white matter injury as well as frank concussion
((Hirad AA, Bazarian JJ, Merchant-Borna K, Garcea FE, Heilbronner S, Paul D,
Hintz EB, van Wijngaarden E, Schifitto G, Wright DW, Espinoza TR, Mahon BZ. A
common neural signature of brain injury in concussion and subconcussion. Sci Adv.
2019 Aug 7;5(8):eaau3460. doi: 10.1126/sciadv.aau3460. eCollection 2019 Aug.
PubMed PMID: 31457074; PubMed Central PMCID: PMC6685720.
)).