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Nerve and muscle disease 

Nerve and muscle disease
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date: 04 July 2022

Disorders affecting the lower cranial nerves – V (trigeminal), VII (facial), IX (glossopharyngeal), X (vagus), XI (accessory) and XII (hypoglossal) – are discussed in the first part of this chapter. The clinical neuroanatomy of each nerve is described in detail, as are disorders – often in the form of lesions – for each nerve.

Trigeminal nerve function may be affected by supranuclear, nuclear, or peripheral lesions. Because of the wide anatomical distribution of the components of the trigeminal nerve, complete interruption of both the motor and sensory parts is rarely observed in practice. However, partial involvement of the trigeminal nerve, particularly the sensory component, is relatively common, the main symptoms being numbness and pain. Reactivation of herpes zoster in the trigeminal nerve (shingles) can cause pain and a rash. Trigeminal neuralgia and sensory neuropathy are also discussed.

Other disorders of the lower cranial nerves include Bell’s palsy, hemifacial spasm and glossopharyngeal neuralgia. Cavernous sinus, Tolosa–Hunt syndrome, jugular foramen syndrome and polyneuritis cranialis are caused by the involvement of more than one lower cranial nerve.

Difficulty in swallowing, or dysphagia, is a common neurological problem and the most important consequences include aspiration and malnutrition (Wiles 1991). The process of swallowing is a complex neuromuscular activity, which allows the safe transport of material from the mouth to the stomach for digestion, without compromising the airway. It involves the synergistic action of at least 32 pairs of muscles and depends on the integrity of sensory and motor pathways of several cranial nerves; V, VII, IX, X, and XII. In neurological practice dysphagia is most often seen in association with other, obvious, neurological problems. Apart from in oculopharyngeal muscular dystrophy, it is relatively rare as a sole presenting symptom although occasionally this is seen in motor neurone disease, myasthenia gravis, and inclusion body myositis. Conversely, in general medical practice, there are many mechanical or structural disorders which may have dysphagia as the presenting feature. In some of the disorders, notably motor neurone disease, both upper and lower motor neurone dysfunction may contribute to the dysphagia. Once dysphagia has been identified as a real or potential problem, the patient should undergo expert evaluation by a clinician and a speech therapist, prior to any attempt at feeding. Videofluoroscopy may be required. If there is any doubt it is best to achieve adequate nutrition through the use of a fine-bore nasogastric tube and to periodically reassess swallowing. Anticholinergic drugs may be helpful to reduce problems with excess saliva and drooling that occur in patients with neurological dysphagia, and a portable suction apparatus may be helpful. Difficulty in clearing secretions from the throat may be helped by the administration of a mucolytic agent such as carbocisteine or provision of a cough assist device.

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