Page 343 - Medicine and Surgery

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Chapter 7: Disorders of cranial and peripheral nerves 339

Function Hypoglossal nerve (XII) lesions
They have motor, sensory and autonomic functions.
Anatomy
Glossopharyngeal receives taste and common sensation
This arises from the hypoglossal nucleus in the medulla,
from the posterior third of the tongue, the oropharynx
and is a motor nerve supplying the muscles of tongue
via the pharyngeal plexus, and the tonsillar fossa and soft
except palatoglossus.
palate.
Vagus carries motor fibres to the muscles of the palate,
pharnyx and larynx. It also carries autonomic innerva- Function
tion to the heart, respiratory tract and gut. Speech, swallowing.

Specific causes
Specific causes
Stroke, bulbar palsy, polio, trauma and tuberculosis.
Central causes include vascular lesions of the medulla,
tumours, syringobulbia and motor neurone disease.
Aneurysms and tumours in the posterior fossa and Clinical features
meningitis may affect the nerves. The left recurrent la- Tongue deviates to side of lesion when patient is asked
ryngeal nerve (a branch of the vagus) may be damaged to stick tongue out. The tongue may appear wasted.
in head and neck surgery, or compressed by hilar lymph
nodes from lung tumours.
Peripheral nerves

Clinical features Lesions of peripheral nerves
Impaired gag reflex (IX forms the sensory component,
Lesions of one or more peripheral nerves cause a char-
X the motor), a hoarse voice and abnormal swallow.
acteristic motor and sensory loss. In some cases there is
a pure motor or pure sensory deficit, but in most there
is a combination of both.
Accessory nerve (XI) lesions Aneuropathy means a pathological process affecting
aperipheral nerve. Damage to the peripheral nerves are
Anatomy
caused by a number of mechanisms, principally
Spinal accessory branch arises from upper cervical cord
demyelination,
segments and passes through the foramen magnum to
axonal loss,
join the cranial accessory branch. They leave the skull
compression or traumatic sectioning of a nerve,
separately through the jugular foramen.
ischaemia and
infiltration.

Function
Mononeuropathies: Involvement of a single nerve.
Cranial nerves join the pharyngeal plexus and supply the
Traumatic peripheral nerve injuries may result from
muscles of the palate, pharynx and larynx. The spinal
compression,penetratingtraumaorclosedfracturesand
part supplies trapezius and sternocleidomastoid.
dislocations. Traumatic nerve damage may result in:
Neuropraxia, a transient loss of physiological function

Specific causes with no loss in continuity and no degeneration. Acute
Polio, syringomyelia, tumours near the jugular foramen. compression of the nerve causes focal (segmental) de-
myelination, but once the compression is relieved, re-
covery is usual within 6 weeks.
Clinical features Axonotmesis, which follows more severe compression
Weakness of lifting ipsilateral shoulder and turning head or traction damage, with Wallerian degeneration of
against resistance towards the contralateral side. the nerve distal to the injury. The time taken to recover