Which of the following is the most likely locus of this lesion? A 40-year-old male who had been suffering from a disorder of unknown origin complains to his physician that he has difficulty in producing a smile from the left side of his face and that he can't salivate or produce tears from the left eye. Further analysis showed some loss of taste and that the affected muscles were flaccid and the eyelids were open.
A. The nucleus of the facial nerve B. Inferior and superior ganglia of cranial nerve IX C. Geniculate ganglion D. Cerebral cortex E. Reticular formation
The answer to this is letter C. What is the geniculate ganglion? This has gotten its name because it somehow looks like a knee that is bent. This is composed of a variety of nerves that are responsible for the responses that the face makes.
The fact that the person is unable to make certain expressions may signify that the geniculate ganglion is affected by it. The other choices available may provide other symptoms if they are affected but at this point, it is letter C that would need to be checked. There are different tests that the patient may undergo just to be sure if this is the part to focus on.
Geniculate ganglion -the nerve affected by this disorder is cranial nerve vii (facial nerve). the cell bodies of origin, which innervate the muscles of facial expression (special visceral efferents), arise from the facial nucleus, which are located in the ventrolateral aspect of the lower pons. the preganglionic parasympathetic neurons, which synapse with postganglionic neurons in the submandibular and pterygopalatine ganglia, arise from the superior salivatory nucleus of the lower pons. the most likely locus of the defect is the geniculate ganglion. the region of the geniculate ganglion and regions adjacent to it contain sensory, skeletal, and visceral motor components of this nerve. therefore, disruption of this nerve in the region of the geniculate ganglion will produce the constellation of deficits described in this case. the other choices are not appropriate. cranial nerve ix is not involved. neither are the regions of the reticular formation and facial nucleus, because lesions at either of these locations could not account for the totality of deficits described in this case. the lesion could not have involved the cerebral cortex because the motor effects were described as a flaccid facial paralysis. a cortical lesion does not produce flaccidity of these muscles.