Cranial Nerves IX, X, XII: The Mouth

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Cranial Nerves IX, X, XII

The Mouth

BACKGROUND

Glossopharyngeal nerve: IX

• Sensory: posterior one-third of tongue, pharynx, middle ear.

• Motor: stylopharyngeus.

• Autonomic: to salivary glands (parotid).

Vagus nerve: X

• Sensory: tympanic membrane, external auditory canal and external ear.

• Motor: muscles of palate, pharynx, larynx (via recurrent laryngeal).

• Autonomic: afferents from carotid baroreceptors, parasympathetic supply to and from thorax and abdomen.

Hypoglossal nerve: XII

• Sensory: none.

• Motor: intrinsic muscles of the tongue.

MOUTH AND TONGUE: WHAT TO DO

Ask the patient to open his mouth.

Look at the gums.

• Are they hypertrophied?

Look at the tongue.

• Is it normal in size?

• Are there rippling movements (fasciculations)?

• Is it normal in colour and texture?

Ask the patient to put out his tongue.

• Does it move straight out or deviate to one side?

COMMON MISTAKES

• Small rippling movements of the tongue are normal when the tongue is protruded or held in a particular position.

• Fasciculations need to be looked for when the tongue is at rest in the mouth.

To assess weakness

Ask the patient to push his tongue into his cheek and test the power by pushing against it; repeat on both sides.

Test repeated movements

Ask the patient to put his tongue in and out as fast as he can, and move it from side to side. Look at the speed of tongue movement.

Ask the patient to say ‘ticker ticker ticker’ as fast as he can.

Test speech

See dysarthria (Chapter 2).

MOUTH: WHAT YOU FIND AND WHAT IT MEANS

• Gum hypertrophy: phenytoin therapy.

• Red, ‘beefy’ tongue: vitamin B₁₂ deficiency.

• Large tongue: amyloidosis, acromegaly, congenital hypothyroi- dism.

• Saliva pooling in mouth: indicates swallowing difficultly.

• Small tongue: with fasciculations = bilateral lower motor neurone lesion; motor neurone disease (progressive bulbar palsy type), basal meningitis, syringobulbia.

• Small tongue: with reduced speed of movements = bilateral upper motor neurone lesion—often associated with labile emotions, increased jaw jerk: pseudobulbar palsy.

• Small tongue: with fasciculations and reduced speed of movements = mixed bilateral upper and lower motor neurone lesions; motor neurone disease (progressive bulbar palsy type).

• Tongue deviates to one side = weakness on the side it moves towards.

– With unilateral wasting and fasciculation: unilateral lower motor neurone disease (rare). Causes: syringomyelia, basal meningitis, early motor neurone disease, foramen magnum tumour.

– With normal bulk: unilateral upper motor neurone weakness (common)—associated with hemiparesis: strokes, tumours.

• Tongue moves in and out on protrusion (‘trombone’ tremor): cerebellar disease, essential tremor, extrapyramidal syndromes.

PHARYNX: WHAT TO DO

Look at the position of the uvula.

• Is it central?

If you cannot see the uvula, use a tongue depressor.

Ask the patient to say ‘Ahh’.

Look at the uvula.

• Does it move up centrally?

• Does it move over to one side?

Additional testing:

If the patient is alert and co-operative and sitting up and swallowing appears safe, ask the patient to swallow (provide a glass of water).

• Watch for smooth coordination of action.

– if there are two phases, with a delay between the oral and pharyngeal phase or

– if swallowing is followed by coughing or breathlessness, which suggest aspiration.

GAG REFLEX: WHAT TO DO

Afferent: glossopharyngeal nerve. Efferent: vagus.

• Touch the pharyngeal wall behind the pillars of the fauces (Fig. 13.1).

Figure 13.1 The mouth

• Watch the uvula; it should lift following the stimulus.

• Ask the patient to compare the sensation between two sides.

PHARYNX AND GAG REFLEX: WHAT YOU FIND

• Uvula moves to one side: upper or lower motor lesion of vagus on the other side.

• Uvula does not move on saying ‘ahh’ or gag: bilateral palatal muscle paresis.

• Uvula moves on saying ‘ahh’ but not on gag, with reduced sensation of pharynx: IX palsy (rare).

LARYNX: WHAT TO DO

Ask the patient to cough.

Listen to the onset.

• Explosive or gradual?

Listen to the speech (see Chapter 3).

• Are volume and quality normal?

• Does the speech fatigue?

Laryngoscopy

Direct visualisation of the vocal cords can be achieved through laryngoscopy, which allows the position of the vocal cords and their movement to be assessed. This normally requires an ENT opinion.

LARYNX: WHAT YOU FIND

• Gradual-onset cough—bovine cough: suggests vocal cord palsy.

• Bubbly voice and cough: suggests combined cord palsy and pharyngeal pooling due to X nerve lesion.

• Swallow followed by coughing indicates aspiration due to poor airway protection: suggests X nerve lesion.

• Unilateral cord palsy: recurrent laryngeal palsy or vagal lesion.

PHARYNX AND LARYNX: WHAT IT MEANS

• Tenth nerve palsy may be due to lesions in the medulla: look for associated ipsilateral cerebellar signs, loss of pain and temperature in the face on the same side and on the body on the opposite side, and an ipsilateral Horner’s (lateral medullary syndrome).

– Extramedullary and intracranial: look for associated XI cranial, IX cranial nerves.

– N.B. Left-sided recurrent laryngeal palsy may arise from mediastinal or intrathoracic pathology.

• Bilateral lower motor neurone X occurs in progressive bulbar palsy (a variant of motor neurone disease (MND)): look for associated tongue fasciculations and mixed upper and lower motor neurone signs without sensory loss in the limbs.

• Bilateral pharyngeal weakness and/or bilateral vocal cord weakness can also occur in myasthenia gravis. This weakness is usually fatigable.

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