Cranial Nerve Disorders

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What are Cranial Nerve Disorders?

Cranial nerves are a set of twelve nerves that emerge directly from the brain and are connected to your face, neck and torso. They are responsible for sensory and motor function control in the head and neck which include vision, hearing, taste, smell, facial expressions, and swallowing. Every cranial nerve serves a distinct purpose and is vital for sensory and motor coordination.

Cranial nerve disorders, also known as cranial neuropathy, are ailments that impair the functioning of the cranial nerves. These conditions can interfere with sensory or motor functions in the head and neck. They can be caused by disease, injury or other underlying conditions like diabetes, and often affect your ability to move, feel, taste, smell and hear.

A tumour pressing against the olfactory nerve

Sensory Nerves

Responsible for your senses, such as smell, hearing and touch.

Motor Nerves

Responsible for movement and function of your muscles or glands.

Special Senses

The olfactory nerve, the optic nerve, the facial nerve, the vestibulocochlear nerve, the glossopharyngeal nerve, and the vagus nerve are responsible for conveying sensations to the brain.

What are the Functions of Different Cranial Nerves?

Olfactory Nerve – Transmits sensory information to the brain regarding smells and sense of taste.
Optic Nerve – The sensory nerve that involves eyesight.
Oculomotor Nerve – This nerve helps with controlling eye muscle movements.
Trochlear Nerve – Powers the contralateral superior oblique muscle, which enables the eye to point inward and downward.
Trigeminal Nerve – The largest cranial nerve that has both sensory and motor functions. It sends information to different areas of the face, from the forehead to the jaw. It also provides sensations of the face, nose and mouth.
Abducens Nerve – Facilitates the lateral rectus muscle, one of the extraocular muscles, to move the gaze outward.
Facial Nerve – This nerve serves both sensory and motor functions in charge of facial expressions, salivary glands, tear-producing glands, and ear sensations.
Vestibulocochlear Nerve – This nerve is responsible for the sense of hearing and balance.
Glossopharyngeal Nerve – The nerve is involved in motor and sensory functions for swallowing and sensations of the throat and taste.
Vagus Nerve – The longest and most complex nerve, responsible for various sensory and motor functions, is part of the circuit that manages the digestive tract, urogenital tract, respiration and heart rate functioning. It also controls changes in the voice.
Accessory Nerve – Responsible for managing certain shoulder muscles.
Hypoglossal Nerve – Responsible for controlling muscles of the tongue.

What are the Types of Cranial Nerve Disorders?

There are many forms of cranial nerve disorders, which are often classified according to the specific nerve that is affected. Some of them include:

Bell’s Palsy

This is a disorder characterised by injury to the 7th cranial nerve, also known as the facial nerve. It often leads to the weakening or paralysis of facial muscles. You may feel pain and discomfort on one side or all over your face or head.

Microvascular Cranial Nerve Palsy

This is a condition that occurs due to a nerve injury in the eye. It is more common among the elderly as well as patients with high blood pressure or diabetes.

Third Cranial Nerve Palsy

Third cranial nerve palsy, also known as ‘oculomotor nerve palsy,’ is a condition that occurs due to damage or illness to the third cranial nerve. This nerve controls the actions of four external eye muscles, which are responsible for moving the eye up and down, rotating it outward and downward toward the ear, as well as turning it inward. Moreover, the third cranial nerve influences eye-focusing abilities, upper eyelid posture, and pupil constriction. Third cranial nerve palsy can lead to complete or partial paralysis of the eye muscles, as the third cranial nerve controls many of them.

Fourth Nerve Palsy

Fourth nerve palsy is caused by injury to the fourth cranial nerve, which affects the superior oblique muscle. This condition may have subtle symptoms that are only evident when the patient walks down a flight of stairs with a tilted head.

Abducens Palsy

This condition, also known as sixth nerve palsy, occurs due to damage to the sixth nerve, which controls horizontal eye movement.

Hemifacial Pain and Spasm

This disorder is characterised by the involuntary twitching of the muscles on one or both sides of the face. It could be caused by nerve damage or a tumour.

Trigeminal Neuralgia

Trigeminal neuralgia, also known as tic douloureux, is a disorder that can cause severe pain on one side of the face, akin to an electric shock. It affects the trigeminal nerve or the fifth cranial nerve, which transmits sensation and nerve signals to specific areas of the head and face. Pain can be triggered by even slight contact, such as when you brush your teeth or apply makeup. Trigeminal neuralgia is known as a chronic pain disorder, as it can persist for a long time.

At first, people with trigeminal neuralgia may experience brief, minor pain episodes. However, as the condition gets worse, it can lead to more frequent and prolonged episodes of pain. Trigeminal neuralgia is a form of neuropathic pain that can be induced by an injury or nerve lesion.

A tumour pressing against the olfactory nerve

Acoustic Tumours

Acoustic neuroma, also known as a vestibular schwannoma, is a type of benign (non-cancerous) brain tumour. It is a growth in the brain that typically develops slowly over time and does not spread to other areas of the body. As acoustic neuroma grows on the nerve responsible for hearing and balance, it can cause difficulties such as hearing loss and unsteadiness.

What Causes Cranial Nerve Disorders?

Depending on the condition, some cranial nerve disorders can be caused by an underlying disease, a tumour, trauma injury, infection, inflammation, or stroke. Certain illnesses can also be birth defects or abnormalities.

Therefore, it is critical that you offer specific information about any associated symptoms, your lifestyle, and your personal and family medical history during your consultation in order to provide a better understanding of your condition.

What are the Symptoms of Cranial Nerve Disorders?

The symptoms you experience may vary greatly and often depend on the affected nerve involved. Some of these symptoms include, but are not limited to:

● Facial weakness
● Facial dropping
● Dropping of the eyelid
● Headaches
● Loss of taste perception

● Severe excruciating pain associated with trigeminal neuralgia
● Unilateral hearing loss
● Tinnitus
● Loss of smell
● Double vision or blurred vision

● Numbness of the face and mouth
● Throataches or irritation
● Hoarseness of voice
● Absence of gag reflex
● Dizziness

When Should I See a Doctor?

Treatment for cranial nerve disorders should begin as soon as they are diagnosed. If you are experiencing any of the symptoms listed above, it is best to schedule an appointment with your neurosurgeon.

What Can I Expect During My First Consultation?

For a detailed consultation, your doctor would begin by asking certain questions to better understand your condition. Some of these may be:

A comprehensive record of your personal and family medical history
Onset of symptoms
Symptoms you experience
Your lifestyle

Your doctor would generally conduct a physical exam and run certain tests for an accurate diagnosis.

How are Cranial Nerve Disorders Diagnosed?

Some diagnostic tests that are typically performed include:

Magnetic Resonance Imaging (MRI) Scan

MRI is a technique that uses high-energy magnetic waves and radio waves to produce detailed images. For example, a higher resolution MRI with contrast and other special sequences (CIS) is routinely used to clarify lower cranial nerves and their relationship with vascular structures to rule out the cause of neuropathy and associated tumours.

Nerve Conduction Velocity (NCV) Test and Electromyography (EMG)

It is a procedure in which a needle is inserted into the muscle to assess electrical activity in the area. NCV and EMG tests are crucial modalities for the functional assessment of nerve fibres and their innervation.

Audiometry

Audiometry is a painless procedure that assesses your hearing capabilities by exposing you to various frequencies in a controlled environment. This helps diagnose acoustic tumours.

Diagnostic tests performed on patients are primarily determined by the initial consultation and the patient’s symptoms.

Can Cranial Nerve Disorders be Cured?

This depends on the type of cranial nerve disorder the patient has. While some cranial neuropathies heal on their own, others may need medication, with more severe cases requiring surgery.

If the patient has any other underlying ailments, such as diabetes, high blood pressure, or specific infections, they must be treated and managed first. Changes in lifestyle may also be necessary for condition management.

How are Cranial Nerve Disorders Treated?

Treatment of cranial nerve disorders mainly depends on the type, severity, and location of the disease.

Medical Treatments

Certain conditions can be effectively managed with medication:

Trigeminal neuralgia is treated with carbamazepine or phenytoin.

Bell’s palsy is treated with steroid medication.

Third nerve palsy or oculomotor nerve palsy caused by diabetes can be medically treated.

Surgical Treatments

• Microvascular Decompression

This is a minimally invasive (keyhole) approach that addresses trigeminal neuralgia symptoms by creating a cushion between the cranial nerve and vessel to alleviate pressure. A small keyhole incision is made behind the ear. Using sophisticated imaging and an endoscope or microscope, minute pads of Teflon are inserted between the nerve and the vessel to relieve nerve irritation.

Alternatively, gamma knife surgery (radiosurgery) can alleviate pain by providing targeted radiation doses to the root entry of the nerve.

• Excision of Cranial Nerve Sheath Tumours

In some cases, the cranial nerve sheath tumour is excised via a minimally invasive microscopic or endoscopic procedure. Due to the proximity of the neurovascular structures, this requires a high level of competence from the neurosurgeon.

Small tumours (less than 2.5cm) can also be treated with gamma knife radiosurgery.

Summary

Cranial nerve disorders can lead to serious conditions such as dysphagia, severe pain, and other symptoms. As early diagnosis facilitates early treatment, if you experience symptoms of a cranial nerve disorder, do not hesitate to reach out to us. Our team will help you properly manage these symptoms or provide tailored treatment.