A 28-year-old man experiences worsening tinnitus and hearing loss. MRI of the brain reveals bilateral vestibular schwannomas. Genetic testing confirms a diagnosis of neurofibromatosis type 2. Additional imaging reveals a small meningioma at the C5 spinal level impinging upon the medial portion of the dorsal columns. Which of the following is the most likely earliest clinical manifestation of this lesion?

Question

A 28-year-old man experiences worsening tinnitus and hearing loss.  MRI of the brain reveals bilateral vestibular schwannomas.  Genetic testing confirms a diagnosis of neurofibromatosis type 2.  Additional imaging reveals a small meningioma at the C5 spinal level impinging upon the medial portion of the dorsal columns.  Which of the following is the most likely earliest clinical manifestation of this lesion?

Quizplus · Accepted Answer

This patient's lesion is affecting the dorsal columns, which convey vibration and proprioception sensation as well as fine touch (ie, 2-point discrimination). They are formed by incoming afferent axons of first-order neurons and are arranged topographically (ie, medial fibers from lower spinal levels, lateral fibers from higher spinal levels): Gracile fasciculus, located medially, which carries afferent information that enters the spinal cord below T6 (lower half of the body) to the gracile nucleus in the medulla Cuneate fasciculus, located laterally, which carries afferent information that enters the spinal cord above T6 (upper half of the body) to the cuneate nucleus in the medulla Therefore, this patient's midline lesion would affect the most medial fibers (gracile fasciculus) first, resulting in loss of vibration sensation in the toes. (Choice A) A decreased biceps tendon reflex is more commonly associated with radiculopathy (C5 or C6) or other conditions affecting the lower motor neurons. This patient's posterior midline mass is most likely to affect the dorsal columns first before affecting the C5 motor neurons in the anterior horn. (Choices B and C) Loss of crude touch sensation can occur with lesions involving the anterior spinothalamic tract; loss of pain sensation can occur with lesions of the lateral spinothalamic tract. These are located in the anterior portion of the spinal cord. (Choice D) Loss of position sensation in the fingers could occur with a lesion affecting the lateral portion of the dorsal columns (ie, cuneate fasciculus). However, this patient's lesion is located medially and would compress the medial aspect first (eg, toe sensation). Educational objective: The dorsal columns are located in the posterior spinal cord and convey vibration, proprioception, and light touch sensation. Sensation from the lower limbs is carried in the gracile fasciculus, which is located in the medial aspect; sensation from the upper limbs is carried in the cuneate fasciculus, which is located in the lateral aspect.

A 28-Year-Old Man Experiences Worsening Tinnitus and Hearing Loss