Multiple Cranial Neuropathies - Types, Causes, Diagnosis, and Treatment

Introduction

Nerves are important structures in the body. They connect each part of the body with the master organ, which is the brain. Cranial nerves are specialized nerves that originate from the brain or brainstem (the bottom, stalk-like portion of the brain). There are twelve pairs of cranial nerves in the human body. All of them have specific sensory and motor functions. They send electrical signals to the brain to and from different body parts such as the face, neck, and torso.

What Are Cranial Neuropathies?

Cranial neuropathies are caused due to damage to the cranial nerves that affect the ability to feel sensations and impair motor function. Cranial neuropathies often affect the face and eyes as the cranial nerves supply these body areas. If several cranial nerves are damaged at one time, they are termed multiple cranial neuropathies.

What Are the Different Types of Cranial Neuropathies?

The different types of cranial neuropathies are -

1. Bell's Palsy - It is also known as acute facial paralysis of unknown cause. This disease occurs due to damage to the facial nerve (seventh cranial nerve). The facial nerve supplies the entire face. It controls all the muscles of the face and taste sensations of the tongue as well. This condition is characterized by muscle weakness on one side of the face. The affected side of the face appears drooping, and even if the patient smiles, it looks one-sided. It is caused by facial nerve swelling and inflammation following a viral infection. In severe rare cases, bell's palsy can affect both sides of the face.

2. Microvascular Cranial Nerve Palsy - Microvascular means small blood vessels. This condition occurs due to blockage of the blood vessels that supply the muscles responsible for the movement of the eyes. This neurological condition causes an inability to move the eyes. The brain sends signals to the muscles of the eyes that are carried by the nerves. If the nerves that supply the muscles of the eyes are not getting an adequate supply of blood due to blockage in the small blood vessels, their function gets impaired. Double vision or diplopia (seeing two copies of an image, either side-by-side or up and down) is a characteristic sign of this condition. This disease is common in the elderly, and patients with diabetes and hypertension are at increased risk of developing this disorder.

3. Third Nerve Palsy - The third cranial nerve is the oculomotor nerve. The oculomotor nerve supplies the muscles that control the movement of the eyes and the size (dilation or contraction) of the pupil. The symptoms of third nerve palsy are -

• An enlarged appearance of the pupil of the eye that does not normally respond to light.

• Double vision or diplopia.

• Drooping of eyelids, also known as ptosis.

• Strabismus is the misalignment of the eyeball.

• The patient tilts the head to have a better view of the images. This happens due to difficulties in binocular vision (the ability of the brain to fuse the images seen by both eyes to form a single three-dimensional image).

This condition may be congenital (present before or at birth), it can be caused due to traumatic injury to the face damaging the nerve, or due to compression of the third cranial nerve.

4. Fourth Nerve Palsy - Any disease or injury to the fourth cranial nerve that causes this condition. Paralysis of the superior oblique muscle occurs due to damage to this nerve. The superior oblique muscle helps in the convergence of the eye (the ability to look at the tip of the nose).

5. Sixth Nerve Palsy - Paralysis of the abducens nerve. This nerve helps control eye movements.

What Are the Causes of Cranial Neuropathies?

Cranial neuropathies occur as a result of damage to the cranial nerves. The following factors are responsible for developing cranial neuropathies -

• Uncontrolled Diabetes - An increase in blood sugar levels harms nerve health. Diabetes leads to nerve damage leading to a loss of sensory function.

• High Blood Pressure - Increased blood pressure due to congested blood vessels (fatty deposition in the lumen of the arteries) causes inadequate blood supply to the nerves, which affects their function.

• Head Injuries - Trauma can cause direct injury to the underlying nerve and may even cause compression of the nerves.

• Stroke - Decreased blood and oxygen supply to the brain causes a stroke. This reduced blood supply damages the nerves of the brain and spinal cord.

• Brain Tumors - Pressure from the adjacent tumors causes paralysis of the nerves.

• Infections - Nerve damage is a common post-viral infection. The viruses can damage the nerves.

• Autoimmune Diseases - The conditions in which the immune response of the body attacks its healthy cells are known as autoimmune diseases. Autoimmune conditions such as Guillain-Barre syndrome (the immune system attacks the nerves to cause paralysis of the hands and feet).

• Inflammation in the Body - Inflammation is followed by infections in the body. The nerves get damaged due to inflammation in any part of the body.

• Increased Pressure Inside the Skull - Severe headaches can cause increased pressure in the skull.

What Are the Different Signs and Symptoms of Cranial Neuropathies?

The patient experiences a variety of signs and symptoms depending upon the location where the nerves are affected in the body. The symptoms include -

• Pain in the area where the nerves are damaged.

• Tingling sensation (such as ants crawling).

• The affected area may feel numb upon touching.

• Weakness and paralysis of the muscles of the face.

• The skin overlying the damaged nerves becomes sensitive to touch.

• The patient experiences problems with vision, such as blurred vision or double vision.

• The face appears to droop towards the affected side due to muscle tone and strength loss. In addition, the eyelids appear drooped too.

• Facial expressions may also get affected due to paralysis.

How Are Multiple Cranial Neuropathies Diagnosed?

The following tests are carried out to diagnose the neuropathies -

• Routine Physical Examination - The physician will perform a detailed physical examination, including a nervous system examination, to assess the sensory and motor functions, reflexes, and mental status of the patient.

• Blood Tests - These may be required in cases of infections or if the patient has diabetes.

• Brain Imaging Scans - MRI (magnetic resonance imaging) and CT (computed tomography) scans are useful in visualizing the abnormalities in the brain. Suppose there is a presence of any anomaly, such as brain tumors, it can be seen on the scan.

• Electromyography - This test is done to assess the electrical activity of the muscles when they are at rest and when in function.

• Nerve Conduction Velocity Test - It is also known as the nerve conduction study. This test checks how fast an impulse moves through the nerves. In the case of neuropathies, there will be a slower rate of conduction of impulses.

• Angiography - A special X-ray to observe the heart and blood vessels. Patients with chronic hypertension require this test to visualize abnormalities in the heart and associated blood vessels.

• Biopsy of The Skin And Nerves - A small piece of tissue is obtained from the affected part of the body, and the nerves underlying it are observed for any damage.

• Cerebrospinal Fluid Examination (CSF Studies) - A lumbar puncture or spinal tap (the spinal fluid is obtained by inserting a special needle into the spinal space) is performed to extract the cerebrospinal fluid for diagnosing viral infections.

How Are Multiple Cranial Neuropathies Treated?

1. Cranial neuropathies should be considered a medical emergency. Any alarming symptoms should be first addressed to the physician.

2. Medications are prescribed to treat infections, swelling, inflammation, and pain caused by neuropathies.

3. Surgery is suggested for patients with severe symptoms and when the nerve damage can be reversed. However, in some cases, the damage will be permanent and cannot be treated by medications and surgery.

4. Systemic diseases like diabetes and hypertension must be diagnosed and treated promptly to avoid further complications. Medications should be prescribed for the same.

5. The patient needs to make certain lifestyle modifications as well, such as -

• Maintaining a healthy diet that consists of fresh fruits and vegetables and foods rich in antioxidants such as berries and citrus fruits.

• Exercising regularly and having healthy physical activity every day.

• Abstaining from consumption of alcohol and cigarette smoking.

Conclusion

Identifying and treating underlying causes of neuropathy are critical factors in managing cranial neuropathies. Cranial neuropathies should be considered a medical emergency. All alarming symptoms need to be reported immediately to the physician. The earlier this disease is diagnosed, the sooner the treatment will begin, and nerve damage can be controlled efficiently. Avoiding all possible risk factors contributing to high blood pressure and stroke will help manage neuropathy. Uncontrolled diabetes must be treated with medications to avoid further complications. Patients diagnosed with multiple neuropathies need special care and support from the healthcare provider to lead a better life.