Does the Chorda Tympani in Man Contain Secretory Fibers for the Parotid Gland?

Abstract

Twenty-two representative cases were studied with respect to the relationship of the chorda tympani to the secretory capacity of the parotid gland. The chorda tympani had been severed or otherwise damaged in 13 cases, the majority of which showed, on gustatory stimulation, a reduction of up to 50 per cent in the parotid secretion. Of six patients with peripheral facial paralysis, four had manifest chorda tympani involvement, and in these cases too the parotid secretion was reduced. One patient with unilateral glossopharyngeal nerve paralysis involving the tympanic nerve, but with an intact chorda tympani function, presented a satisfactory secretory response to gustatory stimulation even though the principal secretory nerve of the parotid was paralyzed.

In two cases, one side of the tongue segment innervated by the chorda tympani was anesthetized with 0.3 M pantocaine, yet the ipsilateral parotid secretion on gustatory stimulation was not appreciably decreased. This finding suggests that the loss of taste per se does not account for the observed parotid secretory impairment in chorda tympani paralysis.

It has long been known that the chorda tympani is the principal secretory nerve of the submandibular gland; but our studies indicate that in all probability it also contains secretory fibers for the parotid gland and that these are frequently as important as the tympanic nerve and plexus (Jacobson's anastomosis). Although the latter nerve has always been regarded as the secretory nerve of the parotid, the question whether this in an invariable rule still remains open.

That the innervation varies is evident from cases 7, 8 and, to some degree, 9 (Table 1), where, despite severance of the chorda tympani, the parotid response to gustatory stimulation was not demonstrably impaired.

The secretory communication between the chorda tympani and the parotid probably lies in the region distal to the tympanic cavity. Further anatomic and physiologic studies are required, however, before this question can be definitively resolved.