Oculomotor nerve schwannoma
Left third cranial nerve palsy
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A vividly enhancing nodule is in line with the oculomotor nerve, and most likely represents a schwannoma. Note the "down and out" pupil - although care should be taken when interpreting this as if the scan was performed with eyes closed, then this may merely represent discongugate gaze.
Although schwannomas most commonly affect the vestibular cochlear nerve (see acoustic schwannoma) they can involve any of the cranial nerves (except CN I and II). In this case oculomotor nerve is affected.
Histological proof is often not available for some of these tumors as until mass effect necessitates it, resection will result in a cranial nerve palsy and in this case diplopia etc...