National Physical Therapy Examination (NPTE) Practice Exam

Which cranial nerve is most likely involved if a patient has difficulty reading and descending stairs?

1. Optic (CN II)

2. Oculomotor (CN III)

3. Trochlear (CN IV)

4. Abducent (CN VI)

The correct answer is: Trochlear (CN IV)

The cranial nerve most likely involved in a patient's difficulty with reading and descending stairs is the Trochlear nerve (CN IV). The Trochlear nerve controls the superior oblique muscle, which is responsible for downward and lateral movement of the eye. When there is dysfunction or impairment of this nerve, it can result in vertical misalignment of the eyes, leading to issues with depth perception and coordination, particularly in tasks that require precise visual adjustment, such as reading or navigating stairs. The symptoms of difficulty reading are likely related to problems with visual tracking or eye alignment, making it hard for the patient to focus on text. Additionally, descending stairs requires a coordinated visual and muscular response to judge the height and position of each step, which can be compromised if the downward gaze is affected. Other cranial nerves listed may contribute to various aspects of vision or eye movement but are less specifically associated with the specific challenges mentioned in the question. For example, the Optic nerve (CN II) is primarily responsible for visual acuity but does not control eye movement. The Oculomotor nerve (CN III), while it does affect several eye muscles, is typically involved in controlling the majority of eye movements and pupil response rather than the specific action of looking downward.