The anatomy of the midbrain (2023)

The midbrain acts as a relay system, transmitting information needed for vision and hearing. It also plays an important role in motor movements, pain and the sleep-wake cycle.

The midbrain, also known as the midbrain, is part of the central nervous system. It is located below the cerebral cortex and at the top of the brainstem.

Anatomy

The midbrain is the upper region of the brainstem.

Structure

Your brainstem connects your brain to your cervical spinal cord (neck) and consists of three main parts:

• midbrain
• bridges
• elongated medulla

(Sometimes themidbrainalso considered part of the brainstem.)

Together, these three parts regulate various involuntary functions such as breathing, heart rate and blood pressure. Your brainstem also plays a crucial role in sleep and consciousness.

Your midbrain can then be divided into two main parts:

• The roof: This anterior surface of the midbrain contains numerous structures, including the reticular formation, the periaqueductal gray matter (PAG), certain cranial nerve nuclei, sensory and motor nerve pathways (the corticospinal and spinothalamic tracts), the red nucleus, the substantia nigra, and the ventral tegmental area (VTA).
• The roof: The posterior surface of the midbrain contains the quadrigeminal bodies, which contain clusters of nerve cells called the superior and inferior colliculus.

Location

The midbrain is about 1.5 centimeters long and lies between the diencephalon (which includes the thalamus and thalamus).hypothalamus) and the bridge.

The midbrain is supplied with blood by the basilar artery and its branches, including the posterior and superior cerebellar arteries.

There are also twobrain nervesno midbrain present:

• ON. oculomotorius (Hirnnerv III)
• OTrochlear nerve (cranial nerve IV).

function

The midbrain is a complex region of the brainstem that performs many functions.

The roof

Structures within the tegment perform these specific functions:

• net-like structure: This highly diverse and integrative area contains a network of nuclei responsible for many vital functions, including arousal, awareness, sleep-wake cycles, coordination of certain movements, and cardiovascular control.
• Periaqueductal gray matter (PAG).: This area plays a key role in processing pain signals, autonomic functioning, and behavioral responses to fear and anxiety. Recently, this structure has been implicated in the control of defense responses associated withPost Traumatic Stress Disorder (PTSD).
• The Brain's Friends: The oculomotor nerve nuclei are responsible for controlling the pupil and most eye movements. Trochlear nerve nuclei innervate the superior oblique muscle of the eye, which abducts, depresses, and inwardly rotates the eye.
• spinothalamic treatment: this main nerve pathway carries information about pain and temperature sensations from the body to the brain's thalamus.
• Corticospinal Treatment: this main nerve pathway carries movement-related information from the brain to the spinal cord.
• red core: This region is involved in motor coordination. It is called the "red" core because of its pink color, which is due to the presence of iron.
• black substance: This area contains nerve cells that make up the neurotransmitter (brain chemical)dopamine. It serves as a relay station for nerve signals responsible for controlling movement.
• Ventral Tegmental Area (VTA): O contains dopamine-producing cell bodies and plays a key role in the reward system.

The roof

nerve cells in itthe superior colliculiVisual signal processingretina of the eyebefore being directed to the occipital lobe at the back of the head. The superior colliculi of the midbrain are also responsible for generating eye movements and neck muscle activity.

Othe lower part of the neckit is responsible for processing auditory signals (hearing) before they pass through the thalamus and finally to the primary auditory cortex in the temporal lobe. In addition to sound localization, the inferior colliculus is responsible for:

• Creating the startle response
• Alignment of the body to specific stimuli
• Distinction between pitch and rhythm

Associated terms

The midbrain can be affected by a number of different pathological processes, includingAVCB. a tumor, a demyelinating process, an infection, or a neurodegenerative disease.

Examples of specific conditions are:

Oculomotor (third) nerve palsy

Any injury to the midbrain (stroke, tumor, inflammation, infection) can damage the oculomotor nerve, resulting in an eye that looks down and out.

Other symptoms of eye paralysis include:

• a dilated pupil
• drooping eyelid
• Diplopia (double vision)
• inability to adapt

Study palsy of the (fourth) nerve

As with oculomotor nerve palsy, a midbrain injury can cause trochlear nerve palsy. Symptoms of trochlear nerve palsy include:

• upward deviation of the eye
• blurry vision
• diplopia
• Tilting the head to the unaffected side to compensate for visual changes

midbrain syndromes

There are five classic midbrain syndromes:

• Parinaud's syndrome: Also known as dorsal midbrain syndrome, this condition usually results from the mass effect of an adjacent brain.Pineal glandTumor. Symptoms may include looking down at rest, pupils that respond poorly to light, eyelid retraction, and convergence retractionNystagmus(if you have uncontrollable, jerky eye movements)
• Weber's syndrome: This condition, also known as midbrain stroke syndrome and alternating superior hemiplegia, is caused by a stroke in a branch of the basilar or posterior cerebral artery. This results in ipsilateral third nerve palsy (same side) and contralateral weakness (opposite side).
• Claude's syndrome: This condition results from a stroke in the dorsal (upper) tegmentum of the midbrain. This leads to ipsilateral oculomotor palsy with contralateral cerebellumAtaxia(uncoordinated movements).
• benedict syndrome: Like Claude's syndrome, this condition results from a stroke in the tegmentum of the midbrain. In addition to oculomotor nerve palsy and ataxia, there is damage to the corticospinal tract, resulting in contralateral weakness.
• Nothnagel's syndrome: this condition usually results from a midbrain tumor, such as aGlioma. Symptoms include unilateral or bilateral oculomotor nerve palsy and ipsilateral cerebellar ataxia.

Multiple sclerosis

Multiple Sclerosis (MS)occurs when a person's own immune system attacks the insulating covering (myelin) of nerve fibers in the brain, spinal cord, and/or eyes.

When the brainstem is affected, the patient may experience the following symptoms:

• Visual disturbances, including diplopia
• Difficulty swallowing (dysphagia)
• Difficulty speaking (dysarthria)
• Altered sensation or weakness of the face
• hearing difficulties
• Ataxia
• Headaches that resemble a migraine
• Rarely, problems affecting vital signs (for example, breathing or heart rate)

Parkinson disease

Parkinson diseaseit is a progressive neurological condition (meaning the symptoms are subtle at first and slowly get worse). It is caused by the death of dopamine-producing nerve cells in the substantia nigra.

As a result of this dopamine depletion, severalsymptomscan develop, including:

• resting tremors
• slowness of movement
• Stiffness and shuffling gait
• small handwriting
• sleep disorders

congenital malformation

In rare cases, a person's midbrain does not form properly during fetal development. Midbrain dysplasia is one such genetic malformation that results in microcephaly, spasticity, intellectual disability, and seizures.

Treatment

Treatment depends on the specific pathology affecting the midbrain.

For example, patients withTumor cerebralaffecting the midbrain may require surgery, radiation and/or chemotherapy.

in the same way aischemic stroke(caused by a blood clot) in the midbrain may warrant treatment with a drug called a "clot-dissolving" drugTissue-type plasminogen activator. Also, a patient needs a comprehensive evaluation to clarify the cause of the stroke (eg, heart disease, atrial fibrillation, etc.).

From there, several therapies can be indicated, including medication, such asanticoagulantsand rehabilitation therapy (eg, physiotherapy and occupational therapy).

MS-related inflammationof the midbrain usually requires short-term treatment with corticosteroids and long-term treatment with adisease modifying therapy.rehabilitation therapyTreating the symptoms is often warranted.

The treatment ofParkinson diseaserequires participation in physical and occupational therapy and use of medications designed to replace dopamine or optimize the effects of dopamine in the brain (eg, levodopa).