Table of ContentsView AllTable of ContentsAnatomyFunctionAssociated ConditionsTreatment
Table of ContentsView All
View All
Table of Contents
Anatomy
Function
Associated Conditions
Treatment
The midbrain functions as a relay system, transmitting information necessary for vision and hearing. It also plays an important role in motor movement, pain, and the sleep/wake cycle.
The midbrain, also called the mesencephalon, is a part of the central nervous system. It is located below your cerebral cortex and at the top of your brainstem.
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The midbrain is the most superior region of the brainstem.
Structure
Your brainstem connects your brain to your cervical spinal cord (neck) and consists of three main parts:
(Sometimes, thediencephalonis also considered part of the brainstem.)
Together, these three parts work to regulate various involuntary functions, such as breathing, heart rate, and blood pressure. Your brainstem also plays a critical role in sleep and consciousness.
Your midbrain can then be broken down into two main parts:
Location
The midbrain measures around 1.5 centimeters in length and is sandwiched between the diencephalon (which includes the thalamus andhypothalamus) and the pons.
The midbrain receives blood supply from the basilar artery and its branches, including the posterior cerebral artery and the superior cerebellar artery.
There are also twocranial nervespresent in the midbrain:
The midbrain is a complex region of your brainstem that serves many functions.
Tegmentum
The structures within the tegmentum serve these specific functions:
Tectum
Nerve cells withinthe superior colliculiprocess vision signals from theretina of the eyebefore channeling them on to the occipital lobe located at the back of the head. The superior colliculi of the midbrain is also responsible for generating eye movements and neck muscle activity.
Theinferior colliculiis responsible for processing auditory (hearing) signals before they are channeled through the thalamus and eventually to the primary auditory cortex in the temporal lobe. In addition to sound localization, the inferior colliculus is responsible for the following:
Examples of specific conditions include the following:
Oculomotor (Third) Nerve Palsy
Any lesion within the midbrain (stroke, tumor, inflammation, infection) may damage the oculomotor nerve, resulting in an eye that is positioned in a downward and outward direction.
Other symptoms of an oculomotor nerve palsy include:
Trochlear (Fourth) Nerve Palsy
As with an oculomotor nerve palsy, a lesion within the midbrain may cause a trochlear nerve palsy. Symptoms of a trochlear nerve palsy include:
Midbrain Syndromes
There are five classic midbrain syndromes:
Multiple Sclerosis
Multiple sclerosis (MS)occurs when a person’s own immune system attacks the insulating covering (myelin) of nerve fibers in their brain, spinal cord, and/or eyes.
If the brainstem is affected, a patient may experience symptoms like:
MS Brain Lesions and Their Effects
Parkinson’s Disease
As a result of this dopamine depletion, varioussymptomsmay develop, including:
Congenital Malformations
Rarely, a person’s midbrain may not form correctly during fetal development. Midbrain dysplasia is one such genetic malformation that results in microcephaly, spasticity, intellectual disability, and seizures.
Treatment depends on the specific pathology that is affecting the midbrain.
For example, patients with abrain tumorthat affects the midbrain may require surgery, radiation, and/or chemotherapy.
From there, various therapies may be advised including medications, like ananticoagulant, and rehabilitation therapy (e.g. physical and occupational therapy).
MS-related inflammationof the midbrain often requires short-term treatment with corticosteroids and long-term treatment with adisease-modifying therapy. Rehabilitation therapies to manage symptoms is also often warranted.
The treatment ofParkinson’s diseaserequires engaging in physical and occupational therapy and taking medications aimed at replacing dopamine or optimizing dopamine’s action in the brain (e.g., levodopa).
10 Sources
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