10th Cranial Nerve – Tests for the Vagus nerve

Definition:

The use and interpretation of medical examinations to determine the integrity and adequate function of the Vagus nerve (tenth cranial nerve).

The role of Vagal afferent nerves:  in initiating the cough reflex is undisputed.

Test procedure:

The Vagus nerve is usually tested together with the glossopharyngeal and hypoglossal nerves. Instruct the patient to say ‘Ahh’ and assess the soft and hard palates, uvula and tongue looking for any signs of deviations and/or asymmetries.

Following this, instruct the patient to place their hand in front of their mouth and cough.

Test findings (inc Positive & Negative results):

Vagus nerve lesions produce palatal and pharyngeal paralysis, laryngeal paralysis, and abnormalities of oesophageal motility, gastric acid secretion, gallbladder emptying, and heart rate as well as other autonomic dysfunction. Palatal weakness can cause ‘nasal speech’ and nasal regurgitation of food. The palate moves asymmetrically when the patient says ‘Ahh’.

Recurrent nerve palsy results in hoarseness, loss of volume and the typical ‘bovine cough’ presentation with regards Vagus lesions.

With a unilateral lesion, the uvula is drawn to the normal side and the soft palate will be elevated irrespective of the side of the pharynx that is being probed.

Considerations:

An isolated palsy of the Vagus nerve is extremely rare.

Causes include:

  • trauma
  • brainstem lesions
  • tumours in the cerebellopontine angle
  • Gullain-Barré syndrome
  • space occupying lesions
  • dissecting aortic aneurysm