What Is the Eighth Cranial Nerve?

Cranial nerve English control cranialnerve; cranialnerves; cranialneural, cranial nerve is also called "brain nerve". There are 12 pairs of brain nerves in the human body, that is, there are 24 pairs of peripheral nerves that belong to the left and right pairs of nerves emitted from the brain. The 12 pairs of human brain nerves are the olfactory nerve, optic nerve, oculomotor nerve, pulley nerve, trigeminal nerve, abductor nerve, facial nerve, auditory nerve, glossopharyngeal nerve, vagus nerve, paraspinal nerve and hypoglossal nerve. The distribution of these nerves is limited to the head and neck, with the exception of the vagus nerve, which extends to the internal organs of the thorax and abdomen.

Cranial nerve

Cranial nerve English control cranialnerve; cranialnerves; cranialneural, cranial nerve also known as "

There are twelve pairs of cranial nerves in the human body.

The first pair is called

12 pairs of cranial nerves

Cranial nerve symptoms: such as decreased vision, double vision,

Cranial nerve idiopathic cases are common, although many occur in elderly and diabetic patients

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The facial nerve consists of two parts: the motor fibers and the intermediate nerves that innervate the facial muscles. The intermediate nerve consists of sensory and parasympathetic fibers. Facial lesions can be found in the brainstem, skull base, facial nerve canal and its distal end. Because the abductor nucleus and pontine lateral vision center are adjacent to the facial nucleus. Therefore, brainstem lesions involving the facial nerve are often accompanied by cross paralysis consisting of eye abduction or lateral paralysis. Facial nerve damage is mainly manifested as facial paralysis or facial muscle spasm.

Etiology and mechanism

The causes of facial nerve damage are common, including acute non-purulent facial neuritis, shingles, trauma, tumors, vascular disease, infectious mononucleosis, syphilis and otitis media, vascular malformations, and vascular torsion. Its pathogenesis is closely related to the etiology. The pathogenesis of facial neuritis is due to nerve stem fiber edema, compression and ischemia, etc. Trauma and surgery are mostly caused by compression and surgical injury.

Clinical manifestation

1. Facial paralysis: manifested as paralysis of the facial muscles on the side of the disease, disappearance or superficial forehead lines, can not frown forehead and frown, can not close or incomplete closed eyes, when the eye is closed, the paralyzed side of the eyeball turns upwards, exposing the white sclera , Called the Bell phenomenon. The nasolabial sulcus on the affected side became shallow, the corners of the mouth drooped, the cheeks were drawn to the healthy side, and actions such as closing eyes, teething, bulging cheeks, and whistling failed, or could not be completed at all. Due to buccal muscle paralysis, food tends to stay between the teeth and cheeks on the diseased side. Punctal point eversion with the lower eyelid, so that tears can not be absorbed normally and cause overflow. If it invades the tympanic nerve, there will be 2/3 of the tongue's taste disorder.

2. Facial spasm: Most patients with facial spasm develop after middle age, and slightly more women. It starts from one side of the eye and gradually extends to the mouth and all facial muscles. The frontal muscles are less affected. In severe cases, the ipsilateral cervical broad muscles can be involved. For paroxysmal, rapid, irregular twitches. The convulsion lasts for a few seconds at first, and then gradually extends up to 5 minutes or longer, while the interval time gradually decreases, and the convulsions gradually become serious. Severe cases are tonic, causing the ipsilateral eyes not to open, the corners of the mouth being severely skewed to the ipsilateral side, and unable to speak. No positive signs of neurological examination.

Facial nerve palsy

(1) Idiopathic facial palsy (also known as Bell palsy) refers to unilateral peripheral facial palsy with acute onset of unknown cause. Mainly manifested as unilateral typical facial nerve palsy. Before the illness, there was a history of cold wind in the face and ears. According to the acute onset and typical clinical manifestations, diagnosis is usually not difficult.

(Two) acute infectious polyradiculoneuritis

Also known as Guillain-Barre syndrome. Facial nerve damage often causes peripheral facial paralysis. This disease has symmetrical paralysis of the distal limbs and can spread to the trunk. In severe cases, respiratory paralysis can be caused by intercostal and septal ribs. The typical change of cerebrospinal fluid is an increase in protein content, while the number of cells is normal, which is called protein-cell separation phenomenon.

(3) A variety of otitis media, labyrinthitis, mastoiditis, etc. may be complicated by otogenic facial nerve palsy, but there are many symptoms and history of primary disease, such as otitis media or ear pain, abnormal secretions of the external ear canal; Edema caused dizziness and vomiting, while mastoiditis showed local redness, swelling, heat and pain.

(4) Acute infectionslymphocytosis (acuteinfectionslymphocytosis) in addition to facial paralysis, as well as systemic symptoms such as fever, fatigue, anorexia, etc., peripheral blood mononuclear cells significantly increased.

(5) Craniocerebralinjury A craniocerebral fracture can cause facial nerve palsy after a traumatic brain injury. It has a clear history of trauma and features facial facial muscle paralysis. X-rays of the skull (or skull base) can assist diagnosis. Radical mastoidectomy is more likely to damage the facial nerve, and the diagnosis can be determined based on the surgical situation.

(6) Tumors. In addition to facial facial muscle paralysis, tumors in the brainstem and cerebellar pontine angle mainly include auditory nerve damage or other cranial nerve involvement, cerebellar ataxia, and onset of apical papillary edema. Symptoms and signs of involvement. Brainstem evoked potentials, X-rays, and CT scans can assist diagnosis.

(7) Meningitis (cerebralmeningitis) Most of them have a slow onset and have other cranial nerve damage. Cerebrospinal fluid examination has positive findings.

Facial spasm

(1) Facial paralysis There is a history of peripheral facial paralysis, and typical clinical manifestations make diagnosis difficult.

(B) Trigeminal neuralgia. Some patients with trigeminal neuralgia can cause reflex facial muscle twitches, and the corners of the mouth move toward the affected side. They also have flushing, tearing, and salivation, which are called painful twitching. Easily identified based on typical trigeminal neuralgia.

(3) Tumor and motor neuron disease (tumourandmotorneurondisease) Cerebellar pontine horn tumors, facial nerve meningiomas, pontine tumors, medulla cavities, motor neuron diseases, etc. can cause facial muscle spasm, often accompanied by other cranial nerves or long Involve the symptoms and signs of the bundle, and if necessary, perform cerebrospinal fluid, brain sonication, X-ray, XT, MRI scans to assist diagnosis.