From the Guidelines
A pretraumatic 2nd branchial arch nerve issue is associated with a deficit in taste to the anterior two-thirds of the tongue, as the facial nerve (CN VII), which arises from this arch, is responsible for special sensory functions including taste to this region. The 2nd branchial arch gives rise to the facial nerve (cranial nerve VII), which contains branchial motor, visceral motor, general sensory, and special sensory functions, including taste to the anterior two-thirds of the tongue 1. When this nerve is affected, patients can present with a range of deficits, but the specific involvement of taste is directly related to the special sensory function of the facial nerve. This occurs because the facial nerve's special sensory fibers are responsible for transmitting taste information from the anterior two-thirds of the tongue. The underlying anatomy and embryological origin explain this connection - during development, the 2nd branchial arch forms the structures innervated by the facial nerve, including those involved in taste perception.
Key points to consider in this context include:
- The facial nerve (CN VII) is a complex nerve with multiple functions, including special sensory functions like taste 1.
- The 2nd branchial arch is embryologically linked to the development of the facial nerve and its functions.
- Taste to the anterior two-thirds of the tongue is a specific function of the facial nerve, making it a potential deficit in cases of pretraumatic 2nd branchial arch nerve issues.
- Other functions of the facial nerve, such as motor control of facial muscles, can also be affected but are not the primary consideration in this specific context regarding taste.
Given the complexity of the facial nerve and its functions, it's crucial to identify the specific deficit associated with a pretraumatic 2nd branchial arch nerve issue, which, based on the evidence, points towards an issue with taste to the anterior two-thirds of the tongue 1.
From the Research
Deficit Associated with Pretraumatic 2nd Branchial Arch Nerve Issue
The 2nd branchial arch is associated with the development of the facial nerve, which controls various functions including salivation and taste. A pretraumatic issue with the 2nd branchial arch nerve could potentially affect these functions.
- The facial nerve, which is derived from the 2nd branchial arch, provides parasympathetic innervation to the submandibular and sublingual salivary glands via the submandibular ganglion 2.
- Damage to the 2nd branchial arch nerve could lead to abnormalities in salivation, as the parasympathetic innervation to the salivary glands is affected 2.
- The correct answer is therefore related to the function of the submandibular salivary gland, which is controlled by the facial nerve.
- Based on the options provided, the deficit associated with a pretraumatic 2nd branchial arch nerve issue is most likely related to b. Submandibular parasymp.
Rationale for Eliminating Other Options
- Option a. Parotid parasymp is incorrect because the parotid gland is primarily controlled by the glossopharyngeal nerve (9th cranial nerve), which is derived from the 3rd and 4th branchial arches, not the 2nd branchial arch.
- Option c. Lacrimal parasymp is incorrect because the lacrimal gland is controlled by the facial nerve, but its dysfunction would primarily affect tear production, not salivation.
- Option d. Taste to tip of tongue is incorrect because while the facial nerve does carry taste fibers from the anterior two-thirds of the tongue, a pretraumatic 2nd branchial arch nerve issue would more likely affect salivation rather than taste sensation.