INTRODUCTION
The 12 cranial nerves are olfactory nerve I, optic nerve II, oculomotor nerve III, trochlear nerve IV, trigeminal nerve V, abducens nerve VI, facial nerve VII, vestibulocochlear nerve VIII, glossopharyngeal nerve IX, vagus nerve X, spinal accessory nerve XI and hypoglossal nerve XII . Cranial nerves that transmit information from the brain to the eye are optic nerve, oculomotor nerve, trochlear nerve, trigeminal nerve, abducens nerve and facial nerve. The primary function of the cranial nerves in the eye is innervation of muscles in the eye, control of vision, controlling lateral and vertical movements of eyeball in the eye and position and size of eyelids and affecting the direction of gaze . The oculomotor nerve III innervates the eye muscles and permits the eye to rotate within the orbit. The trochlear nerve IV innervates the superior oblique muscles of the eye. Trigeminal nerve V is responsible for innervation of muscles in the sinuses, face and teeth. Cranial nerve VI abducens innervates the lateral rectal muscles of the eye, causing retraction of the eye inside the orbit. The optic nerve transmits visual signals such as perception of color, brightness levels, and visual acuity including contrast from the retina in the eye to brain . Since tilting of head is quite commonly prevalent in case of superior oblique palsy, Zoe is most likely suffering from fourth cranial nerve palsy. This is a condition involving weakening or impairment of the superior oblique muscle . This deformity inhibits the eyes from moving in the same direction. The irregular head positioning permits compensates for the misalignment, the hypothesis is that in case of Zoe, the fourth nerve, i.e. the trochlear nerve may be impaired.
PROCEDURES
The vision of the patient may be evaluated by requesting him to read an eye chart . Peripheral vision is examined by instructing the person to analyze objects or motion from the corners of the eyes. Light detection system may be evaluated by shining a bright light inside each pupil of the eye. Oculomotor system is examined by testing the patient’s ability to move both eyes up and down and inward by requesting the patient to follow a flashlight or any other target object with eyes and assessing for eyelid drooping. Trochlear nerve is examined by instructing the patient to move eyes down and inward. Outward movement of the eyes beyond midline is tested by having the patient move his eyes sideways.
RESULTS
DISCUSSION
Comparing Zoe’s details with the data collected from the normal subject, his visual acuity and peripheral vision seem to be functioning properly. The position of the eyelids, pupillary reflexes and pupil size controlled by the coulometer system are also apparently healthy . The ability of his eyes to move up and down are also clearly un affected, which is also regulated by oculomotor system.
Zoe’s tilting of head to the left, while she concentrates on an object located in the front and her cross-eyed appearance are indicative of a malfunctioning of the fourth nerve, often termed as fourth nerve palsy . The head tilting occurs, in an attempt, to compensate for misalignment of eyes . Since the 3rd cranial nerve, i.e. oculomotor nerve is involved in the movement of eyes up and down and inward, involvement of this component of oculomotor nerve may not be entirely ruled out. But the strabismus and the head tilting are definitive characteristics of fourth nerve palsy, which rationalizes the impairment of trochlear nerve. To confirm the diagnosis further, neural imaging techniques such as magnetic resonance imaging (MRI) may be utilized and detection of the exact cause of impairment may be dissected.
CONCLUSION
The final diagnosis for Zoe’s case is inclined towards unilateral fourth cranial nerve palsy, also called superior oblique palsy, leading to misalignment of eyes. However, impairment of other cranial nerves such as oculomotor cannot be conclusively ruled out in this case, without further confirmation using imaging techniques.
Works Cited
American Academy of Opthalmology. (n.d.). Retrieved April 28, 2016
American Association for Pediatric Ophthalmology and Strabismus. (n.d.). Retrieved April 28, 2016
Healthline. (2015, February 2). Optic nerve. Retrieved from Healthline.com: http://www.healthline.com/human-body-maps/optic-nerve
Marieb, E. N., Hoehn, K. (2011). Human Anatomy and Physiology. Pearson.
Rubin, M. (n.d.). Overview of the Cranial Nerves. merckmanuals.com. Retrieved April 28, 2016
Sanders, R. D. (2009). Cranial Nerves III, IV, and VI. Psyciatry, 6(11): 34-39.
The 12 Cranial Nerves. (n.d.). Retrieved from kenhub.com: https://www.kenhub.com/en/library/anatomy/the-12-cranial-nerves
