In facial nerve palsy of right side Stapedial reflex is absent on:
**Core Concept**
Facial nerve palsy leads to paralysis of the stapedius muscle in the middle ear, resulting in an absent stapedial reflex on the affected side. The stapedial reflex is a protective reflex that helps regulate sound intensity, and its absence can be diagnosed using tympanometry or acoustic reflex testing.
**Why the Correct Answer is Right**
In facial nerve palsy, the nerve supply to the stapedius muscle is compromised, leading to muscle paralysis and an inability to contract in response to sound stimuli. As a result, the stapedial reflex is absent on the affected side. The stapedius muscle plays a crucial role in stabilizing the ossicles in the middle ear and modulating sound intensity. The facial nerve (cranial nerve VII) provides motor innervation to the stapedius muscle.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the stapedial reflex is not affected by lesions of the auditory nerve (cranial nerve VIII). The auditory nerve is responsible for transmitting sound signals to the brain, but it does not have a direct role in the stapedial reflex.
**Option B:** This option is incorrect because the stapedial reflex is not affected by lesions of the trigeminal nerve (cranial nerve V). The trigeminal nerve provides sensory innervation to the face, but it does not have a role in the stapedial reflex.
**Option C:** This option is incorrect because the stapedial reflex is not affected by lesions of the glossopharyngeal nerve (cranial nerve IX). The glossopharyngeal nerve provides sensory innervation to the throat and parasympathetic innervation to the parotid gland, but it does not have a role in the stapedial reflex.
**Clinical Pearl / High-Yield Fact**
An absent stapedial reflex on the right side in a patient with right-sided facial nerve palsy can be a useful clinical sign to diagnose the condition. The stapedial reflex is an important diagnostic tool in otolaryngology and can help differentiate between otitis media and other middle ear disorders.
**Correct Answer:** D