A 71-year-old man comes to the office due to a painful rash on his right forehead. Two days ago, he felt burning pain on his right forehead and today noticed some blisters. On examination, there is a vesicular rash involving the right forehead and right side of the nose. The patient is at risk of blindness in the right eye due to involvement of which of the following cranial nerves?

Question

A 71-year-old man comes to the office due to a painful rash on his right forehead.  Two days ago, he felt burning pain on his right forehead and today noticed some blisters.  On examination, there is a vesicular rash involving the right forehead and right side of the nose.  The patient is at risk of blindness in the right eye due to involvement of which of the following cranial nerves?

Quizplus · Accepted Answer

11ec160b_35b1_8396_9249_119b717aff2b_MD0001_00 This patient has herpes zoster ophthalmicus, which is caused by reactivation of latent varicella-zoster virus (VZV) in the trigeminal ganglion. Following primary VZV infection (ie, chickenpox), the virus migrates via sensory nerves to the cranial nerve and dorsal spinal ganglia, where it lies dormant for years. Reactivation of the virus typically occurs in a single ganglion and causes a painful, vesicular rash in a dermatomal distribution. Viral reactivation within the trigeminal ganglion most often affects the ophthalmic division of the trigeminal nerve (CN V1), leading to development of a vesicular rash within the V1 distribution (eg, unilateral forehead, side of the nose, and periorbital area). Because CN V1 also conveys sensory innervation of the cornea (sensory limb of the corneal/blink reflex), involvement can cause acute keratitis, which can lead to vision loss. Vesicular lesions on the side and tip of the nose (ie, Hutchinson sign) have a high correlation with subsequent eye involvement because the nasociliary branch of CN V1 innervates both the eye and the side/tip of the nose. (Choices A, C, and F) The oculomotor (CN III), trochlear (CN IV), and abducens (CN VI) nerves provide motor innervation to the extraocular muscles. Dysfunction can result in double vision. However, these nerves are not involved in this patient's condition and would not cause blindness if they were. (Choice B) The facial nerve (CN VII) is affected in herpes zoster oticus (Ramsay Hunt syndrome), which classically presents with ear pain, vesicles in the external auditory canal or auricle, and facial paralysis. The facial nerve innervates the orbicularis oculi muscle to close the eye; therefore, patients with facial nerve paralysis are at risk of exposure keratitis, which can lead to blindness. However, this patient's facial nerve is unaffected. (Choice D) In rare instances, zoster can cause blindness due to acute retinal necrosis and/or neuritis of the optic nerve (CN II). However, this patient has zoster involvement of CN V1. Educational objective: Herpes zoster ophthalmicus is caused by viral reactivation within the trigeminal nucleus. It affects the ophthalmic branch of the trigeminal nerve (CN V1) and can lead to blindness due to acute keratitis because V1 conveys sensory information from the cornea. __________ References: Herpes zoster ophthalmicus: acute keratitis. (http://www.ncbi.nlm.nih.gov/pubmed/29794881)

A 71-Year-Old Man Comes to the Office Due to a Painful