Smell, Vision, Taste
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Cranial nerve disease is impaired functioning of one of the twelve cranial nerves. Each cranial nerve controls functions like smell, vision, and balance. Disorders include trigeminal neuralgia, acoustic neuroma, hemifacial spasm, facial nerve disorder, and intractable vertigo.
The 12 Cranial Nerves
- Olfactory: Smell
- Optic: Transmit visual information to the brain
- Oculomotor: Eye movement
- Trochlear: Lateral eye tracking
- Trigeminal: Facial sensation
- Abducens: Lateral eye tracking
- Facial: Facial expressions
- Vestibulocochlear (Acoustic): Hearing and Balance
- Glossopharyngeal: Taste and Swallowing
- Vagus: Gag reflex
- Accessory: Neck muscle control, gag reflex
- Hypoglossal: Tongue movement and Swallowing
Bell’s Palsy
Bell’s Palsy, also referred to as facial palsy, involves sudden weakness or paralysis of the muscles on one side of the face. This condition typically results from swelling or inflammation of the seventh cranial nerve, which is responsible for controlling facial expressions. Because the cranial nerve function is disrupted, one side of the face may droop, causing a one-sided smile and making it difficult to close the eye on the affected side.
Bell’s palsy can develop at any age, and while the precise cause isn’t completely understood, it’s often linked to viral infections or other triggers that may inflame the nerve. Fortunately, most people experience only temporary symptoms and start to see improvement within a few weeks, with full recovery occurring in about six months. However, a small number of individuals may continue to deal with lingering effects of Bell’s palsy for life.
Dilopia
Diplopia, also known as double vision, occurs when a single object is perceived as two separate images. These images can be horizontally, vertically, or diagonally misaligned in relation to each other. In many cases, this condition stems from impaired function in the extraocular muscles or the cranial nerves (particularly the third, fourth, or sixth cranial nerve) that control eye movement. Although both eyes may still function individually, they can’t properly converge to focus on the same target, resulting in the sensation of seeing double.
Diplopia can be one of the earliest indicators of an underlying systemic disease, especially one involving muscle or neurological issues. As a result, it may interfere with a person’s balance, coordination, or reading ability. Identifying and addressing the root causes of diplopia is crucial for effective treatment and for preventing further complications.
Dysphagia
Dysphagia, or difficulty swallowing, often occurs when there is a disruption involving the muscles and cranial nerves (particularly the ninth and tenth cranial nerves) that control the swallowing process. People with dysphagia may feel as though food is stuck in their throat or somewhere behind the sternum (breastbone), extending from the neck down to just above the abdomen. Although it can happen at any age, dysphagia is more common in older adults, and its causes range from mild muscle coordination issues to more complex neurological conditions. Identifying the root cause is essential for effective management and prevention of complications.
External Resource: Dysphagia Research Society
Dysarthria / Stuttering
Dysarthria is a motor speech disorder caused by weakness or impaired coordination of the muscles that produce speech. While it’s sometimes confused with (or referred to as) stuttering, these conditions are not identical. In dysarthria, the underlying problem is often linked to the brain regions or the cranial nerves (such as the hypoglossal nerve controlling the tongue) that regulate speech-muscle movement.
People with dysarthria know what they want to say, but they struggle to form words clearly because the muscles themselves are not functioning properly. In contrast, stuttering involves disruptions in speech fluency—such as repetition of words or sounds—rather than direct weakness or miscoordination in the speech muscles. Dysarthria and stuttering can both arise from developmental factors, inherited brain abnormalities, brain injury, or other neurological or mental health conditions. Effective diagnosis and treatment hinge on identifying the specific root cause behind each individual’s speech challenge.
External Resource: Voice Health Institute
Nystagmus
Nystagmus, commonly referred to as dancing eyes, describes rapid, uncontrollable movements of the eyes. These movements can be vertical, horizontal, or even rotary. They typically result from abnormalities in the brain regions or cranial nerves responsible for coordinating eye muscle function.
Two main types of nystagmus exist:
Infantile nystagmus syndrome (INS), which is present at birth. It’s usually mild and not related to any other medical issue.
Acquired nystagmus, which develops later in life due to factors such as disease, injury, or reactions to certain medications.
Because nystagmus directly impacts eye movement control, it can interfere with focus, balance, and overall visual clarity. Identifying the underlying cause is key to managing or treating this condition effectively.
Ptosis
Ptosis: also known as drooping eyelid, is a condition where one or both eyelids falls to a lower position than is normal. It can be caused by muscle weakness, nerve damage, or looseness of the skin. It often occurs as the result of normal aging, but can also be present at birth or the result of injury or disease.
External Resource: Retina Foundation of the Southwest
Tinnitus
Tinnitus: also known as ringing of the ear, is the perception that one hears ringing when no actual sound is present. Ringing is only one of many sounds that a person may believe he hears. Tinnitus is not a condition itself — it is a symptom of an underlying condition, such as age-related hearing loss, ear injury or a circulatory system disorder.
External Resource: American Tinnitus Association