Runny eyes, taste testing taste

The chorda tympani is generally accepted as the pretrematic branch of the second branchial arch nerve. It passes from second arch tissue to first arch tissue through the tympanic membrane which is itself in the trema between the first and second arches. It contains two types of visceral fibre: afferent (taste) and efferent (parasympathetic). The embryological origin of the petrosal nerves is less certain.

17.6 Clinical notes 1 Frey’s syndrome After parotidectomy, cut ends of postganglionic fibres begin to grow. Should these sprouting fibres find their way into Schwann cells sheaths occupied before surgery by sympathetic fibres, stimuli normally producing salivation will instead induce sweating over the site of the parotid. This is Frey’s syndrome (gustatory sweating) (see Section 14.4).

2 Runny eyes, streaming nose Runny eyes, runny and blocked up nose might be produced by overactivity of the pterygopalatine ganglion. This is why the ganglion is sometimes called the hay fever ganglion although these symptoms are usually allergic.

104 Autonomic components of cranial nerves, taste and smell17.7 Clinical testing of visceral components 1 Salivary glands Ask the patient to suck something bitter (such as a lemon) to provoke salivary secretion. This is sometimes done to try to locate the position of a calculus in the duct of a salivary gland, usually the submandibular, but is not done to test the neural pathways since, as we have said, who cares? 2 Taste Testing taste is possible but hardly worth the trouble.