Nuclear and Infranuclear Lesions of 3,4,6 Cranial Nerve Lesions and their Clinicoradiological Correlation.

Palsies of any of the three cranial nerves supplying the extra ocular muscles have their presentations, disturbing ocular motility. Abnormalities of ocular motility help in the localization of lesions of the cerebral hemispheres, brain stem, cranial nerves (CNs), and even the striated muscle. Only one nerve may be involved or there may be a combination of the three nerves. The palsies are usually acquired. Sometimes palsies can be congenital due to the developmental defect of the nucleus or motor nerve fibers. Oculo motor fibers can be interrupted intraaxially or extraaxially. Lesions can be in the foramens or extra cranial e.g. Intraorbital. All these Oculomotor nerves can be affected in the brainstem (nucleus or fascicular portion)1, in the subarachnoid space, in the cavernous sinus, at the superior orbital fissure, or in the orbit. MRI has become the most useful diagnostic tool in the localization, diagnosis and management of the nuclear and infranuclear lesions of 3, 4, 6 cranial nerves. In conditions like vasculitis and prothrombotic states, laboratory investigations add on to radiological findings and histopathological evaluation is useful when there are therapeutic difficulties. Cranial nerves 3, 4, and 6th palsies can be due to head injury2,26. In many studies head injury is very well correlated with imaging. In this study, we have excluded the head injury patients presenting with 3, 4&6 cranial nerve palsies. CONCLUSION : 1) In this study, there was no sex preponderance. 2) Commonest age group of presentation was 30-40 years. 3) Among the 3,4 and 6 cranial nerves,commonly affected was the 3rd cranial nerve followed by 4th cranial nerve and 6thcranial nerve 4) Among the combinations of cranial nerves, Bilateral 6th nerve involvement and unilateral 3,4,6 cranial nerve involvement were the commonest presentations, followed by bilateral 3,4,6 th cranial nerve involvement. 5) The combinations of 3&4, 3&6 and 4&6 cranial nerve involvement were not found in our series. 6) MRI showed abnormal findings in 70% of the patients, whereas CT showed abnormal findings only in 25% of patients. 7) The commonest cause of nuclear and infranuclear 3.4.6 cranial nerve lesion was Diabetes Mellitus in this study. 8) The commonest cause of imaging negative etiology in this study was Diabetes Mellitus