Trochlear Nerve: What It Is, Location, Function, Mental Health

Table of ContentsView AllTable of ContentsOverviewIs the Trochlear Nerve a Motor or Sensory Nerve?FunctionWhat It ControlsMental Health EffectsHow to Prevent Brain InjuryFrequently Asked Questions

Table of ContentsView All

View All

Table of Contents

Overview

Is the Trochlear Nerve a Motor or Sensory Nerve?

Function

What It Controls

Mental Health Effects

How to Prevent Brain Injury

Frequently Asked Questions

Close

The trochlear nerve is one of 12 pairs of cranial nerves that stem from the brain. Also known as CN IV or cranial nerve 4, it is the fourth set of nerves that extends from the brain. It is a motor nerve that is part of theperipheral nervous system.

The trochlear nerve controls the movements of an eye muscle known as the superior oblique muscle, which connects to the top of the eye.

What to Know About the Trochlear Nerve

The trochlear nerve originates in the brainstem, the bottomportion of the brainlocated near the top of the spine.

The nerve follows a complicated path through the skull, passing through important points, including the trochlear nucleus near the top of the brainstem, the ambient cistern near the protective outer layer of the brain, the cavernous sinus in the middle of the skull, and the orbits of the skull where the eyes are located.

The name of this nerve comes from the structure that the tendon of this nerve passes through, called the trochlea, meaning ‘pulley’ in Latin.

Two types of nerves play different roles in the nervous system: motor and sensory. The trochlear nerve is a motor nerve.

Motor nerves, also known asefferentnerves, carry signals from the brain and spinal cord (thecentral nervous system) to the muscles and glands.The motor nerves are responsible for voluntary movements, such as moving your arm to pick up a cup, and involuntary movements, such as the twitch of a muscle, breathing, heart rate, and digestion.

Sensory nerves, also known asafferentnerves, transmit information from sensory organs, including the skin, eyes, ears, and nose, to the central nervous system.

They take sensory information about touch, sight, sound, taste, pain, light, and pressure and send the signals to the brain for processing. This sensory information may then trigger a response, causing the brain to send a response via the motor nerves.

How the Trochlear Nerve Functions

The trochlear nerve functions as a motor nerve only and does not send sensory signals. It also only controls a single muscle, the superior oblique muscle located in the upper part of the eye.

What Organs Does the Trochlear Nerve Control?

The trochlear nerve does not directly control any organs of the body. Instead, it controls the superior oblique muscle, which allows the eye to rotate downwards, upwards, and from side to side.

Even though the trochlear nerve does not specifically control the eye, it does play an important role in eye movement.

What Are the Mental Health Effects of Damage to the Trochlear Nerve?

Damage to the trochlear nerve can result in a condition known as trochlear nerve palsy or fourth cranial nerve palsy.This condition involves weakness or paralysis of the trochlear nerve, which can affect the ability of the eye to rotate downwards and outwards.

Symptoms of this condition can include:

In addition to affecting vision, this condition can also affect a person’s mental health in a variety of ways. Difficulties with vision can create emotional distress and lead tofeelings of sadnessand frustration.

Other Mental Health EffectsResearch suggests that moderate to severe brain injuries can lead to a variety of mental health effects, including mood problems,personality changes, emotional instability, andimpulsivity. Such injuries are also associated with the onset ofdepressionandpost-traumatic stress disorder (PTSD).

Other Mental Health Effects

Research suggests that moderate to severe brain injuries can lead to a variety of mental health effects, including mood problems,personality changes, emotional instability, andimpulsivity. Such injuries are also associated with the onset ofdepressionandpost-traumatic stress disorder (PTSD).

Vision problems can also impact a person’s social functioning, making it more difficult to attend social activities and events, contributing tosocial isolation and withdrawal.

Trochlear nerve damage can also make it difficult to perform everyday tasks such as reading, driving, and other activities that require precise eye movements, which can take a toll on mental well-being.

However, each person’s situation is different. How a person copes with their condition depends on their social support system, coping mechanisms, and other factors.

In order to prevent damage to the trochlear nerve, it is important to take steps to lower your risk of head trauma.

According to the Centers for Disease Control and Prevention, things you can do to protect yourself frombrain injuryinclude the following:

Be sure to seek medical attention if you do experience a blow to the head or other type of injury.

Frequently Asked QuestionsPeople with trochlear nerve damage will sometimes tilt their heads in order to try to merge the double images they see. An older term sometimes used to refer to this nerve was the ‘pathetic" nerve due to the ‘dejected’ appearance of people with trochlear nerve damage. However, this term is no longer used, and it is referred to as either the trochlear nerve or the fourth cranial nerve.The trochlear nerve is sometimes referred to as the smallest nerve because it contains the fewest number of axons in comparison to other cranial nerves. Despite this, the trochlear nerve takes a longer path than other cranial nerves.

People with trochlear nerve damage will sometimes tilt their heads in order to try to merge the double images they see. An older term sometimes used to refer to this nerve was the ‘pathetic" nerve due to the ‘dejected’ appearance of people with trochlear nerve damage. However, this term is no longer used, and it is referred to as either the trochlear nerve or the fourth cranial nerve.

The trochlear nerve is sometimes referred to as the smallest nerve because it contains the fewest number of axons in comparison to other cranial nerves. Despite this, the trochlear nerve takes a longer path than other cranial nerves.

How a Head Injury Can Affect Your Mental Health

10 SourcesVerywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Tubbs RS, Veith P, Griessenauer CJ, Loukas M, Cohen-Gadol AA.A new segment of the trochlear nerve: cadaveric study with application to skull base surgery.J Neurol Surg B Skull Base. 2014;75(1):8-10. doi:10.1055/s-0033-1349787Kim SY, Motlagh M, Naqvi IA.Neuroanatomy, cranial nerve 4 (trochlear). In:StatPearls[Internet]. Treasure Island (FL): StatPearls Publishing; 2023.National Cancer Institute.The peripheral nervous system.American Association for Pediatric Ophthalmology and Strabismus.Anatomy of the eye.Oh SY, Oh SY.Clinical outcomes and aetiology of fourth cranial nerve palsy with acute vertical diplopia in adults.Eye (Lond). 2020;34(10):1842-1847. doi:10.1038/s41433-019-0749-8American Association for Pediatric Ophthalmology and Strabismus.Fourth nerve (superior oblique) palsy.Howlett JR, Nelson LD, Stein MB.Mental health consequences of traumatic brain injury.Biol Psychiatry. 2022;91(5):413-420. doi:10.1016/j.biopsych.2021.09.024Shah K, Frank CR, Ehrlich JR.The association between vision impairment and social participation in community-dwelling adults: a systematic review.Eye (Lond). 2020;34(2):290-298. doi:10.1038/s41433-019-0712-8Centers for Disease Control and Prevention.Traumatic brain injury and concussion: Prevention.Cohen RA.Trochlear nerve. In: Kreutzer JS, DeLuca J, Caplan B, eds.Encyclopedia of Clinical Neuropsychology. Springer New York; 2011:2560-2561. doi:10.1007/978-0-387-79948-3_1408

10 Sources

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Tubbs RS, Veith P, Griessenauer CJ, Loukas M, Cohen-Gadol AA.A new segment of the trochlear nerve: cadaveric study with application to skull base surgery.J Neurol Surg B Skull Base. 2014;75(1):8-10. doi:10.1055/s-0033-1349787Kim SY, Motlagh M, Naqvi IA.Neuroanatomy, cranial nerve 4 (trochlear). In:StatPearls[Internet]. Treasure Island (FL): StatPearls Publishing; 2023.National Cancer Institute.The peripheral nervous system.American Association for Pediatric Ophthalmology and Strabismus.Anatomy of the eye.Oh SY, Oh SY.Clinical outcomes and aetiology of fourth cranial nerve palsy with acute vertical diplopia in adults.Eye (Lond). 2020;34(10):1842-1847. doi:10.1038/s41433-019-0749-8American Association for Pediatric Ophthalmology and Strabismus.Fourth nerve (superior oblique) palsy.Howlett JR, Nelson LD, Stein MB.Mental health consequences of traumatic brain injury.Biol Psychiatry. 2022;91(5):413-420. doi:10.1016/j.biopsych.2021.09.024Shah K, Frank CR, Ehrlich JR.The association between vision impairment and social participation in community-dwelling adults: a systematic review.Eye (Lond). 2020;34(2):290-298. doi:10.1038/s41433-019-0712-8Centers for Disease Control and Prevention.Traumatic brain injury and concussion: Prevention.Cohen RA.Trochlear nerve. In: Kreutzer JS, DeLuca J, Caplan B, eds.Encyclopedia of Clinical Neuropsychology. Springer New York; 2011:2560-2561. doi:10.1007/978-0-387-79948-3_1408

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Tubbs RS, Veith P, Griessenauer CJ, Loukas M, Cohen-Gadol AA.A new segment of the trochlear nerve: cadaveric study with application to skull base surgery.J Neurol Surg B Skull Base. 2014;75(1):8-10. doi:10.1055/s-0033-1349787Kim SY, Motlagh M, Naqvi IA.Neuroanatomy, cranial nerve 4 (trochlear). In:StatPearls[Internet]. Treasure Island (FL): StatPearls Publishing; 2023.National Cancer Institute.The peripheral nervous system.American Association for Pediatric Ophthalmology and Strabismus.Anatomy of the eye.Oh SY, Oh SY.Clinical outcomes and aetiology of fourth cranial nerve palsy with acute vertical diplopia in adults.Eye (Lond). 2020;34(10):1842-1847. doi:10.1038/s41433-019-0749-8American Association for Pediatric Ophthalmology and Strabismus.Fourth nerve (superior oblique) palsy.Howlett JR, Nelson LD, Stein MB.Mental health consequences of traumatic brain injury.Biol Psychiatry. 2022;91(5):413-420. doi:10.1016/j.biopsych.2021.09.024Shah K, Frank CR, Ehrlich JR.The association between vision impairment and social participation in community-dwelling adults: a systematic review.Eye (Lond). 2020;34(2):290-298. doi:10.1038/s41433-019-0712-8Centers for Disease Control and Prevention.Traumatic brain injury and concussion: Prevention.Cohen RA.Trochlear nerve. In: Kreutzer JS, DeLuca J, Caplan B, eds.Encyclopedia of Clinical Neuropsychology. Springer New York; 2011:2560-2561. doi:10.1007/978-0-387-79948-3_1408

Tubbs RS, Veith P, Griessenauer CJ, Loukas M, Cohen-Gadol AA.A new segment of the trochlear nerve: cadaveric study with application to skull base surgery.J Neurol Surg B Skull Base. 2014;75(1):8-10. doi:10.1055/s-0033-1349787

Kim SY, Motlagh M, Naqvi IA.Neuroanatomy, cranial nerve 4 (trochlear). In:StatPearls[Internet]. Treasure Island (FL): StatPearls Publishing; 2023.

National Cancer Institute.The peripheral nervous system.

American Association for Pediatric Ophthalmology and Strabismus.Anatomy of the eye.

Oh SY, Oh SY.Clinical outcomes and aetiology of fourth cranial nerve palsy with acute vertical diplopia in adults.Eye (Lond). 2020;34(10):1842-1847. doi:10.1038/s41433-019-0749-8

American Association for Pediatric Ophthalmology and Strabismus.Fourth nerve (superior oblique) palsy.

Howlett JR, Nelson LD, Stein MB.Mental health consequences of traumatic brain injury.Biol Psychiatry. 2022;91(5):413-420. doi:10.1016/j.biopsych.2021.09.024

Shah K, Frank CR, Ehrlich JR.The association between vision impairment and social participation in community-dwelling adults: a systematic review.Eye (Lond). 2020;34(2):290-298. doi:10.1038/s41433-019-0712-8

Centers for Disease Control and Prevention.Traumatic brain injury and concussion: Prevention.

Cohen RA.Trochlear nerve. In: Kreutzer JS, DeLuca J, Caplan B, eds.Encyclopedia of Clinical Neuropsychology. Springer New York; 2011:2560-2561. doi:10.1007/978-0-387-79948-3_1408

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