1. Oculomotor nerve (III) : The nuclear complex of the 3rd (oculomotor) nerve is situated in the midbrain at the level of the superior colliculus, ventral to the Sylvian aqueduct .It is composed of thefollowing paired and unpaired subnuclei.
• Levator subnucleus is an unpaired caudal midline structure which innervates both levator muscles. Lesions confined to this area will therefore give rise to bilateral ptosis.
• Superior rectus subnuclei are paired: each innervates the respective contralateral superior rectus. A nuclear 3rd nerve palsy will spare the ipsilateral,and affect the contralateral, superior rectus.
• Medial rectus, inferior rectus and inferior oblique subnuclei are paired and innervate their corresponding ipsilateral muscles. Lesions confined to the nuclear complex are relatively uncommon. The most frequent causes are vascular disease, primary tumours and metastases. Involvement of the paired …show more content…
Normal left abduction.
5. Normal left depression.
6. Normal left elevation.
Abnormal head posture avoids diplopia which is vertical, torsional and worse on looking down,contralateral head tilt to the right when trying to inert the eye,To alleviate the inability to depress the eye is adduction,the face is turned to the right and the chin is slightly depressed.
Causes of isolated 4th nerve palsy:
1. Congenital: lesions are common, although symptoms may not develop until decompensation occurs in adult life.Unlike acquired lesions patients are not usually aware of the torsional aspect.
2. Trauma frequently causes bilateral 4th nerve palsy.The long and slender nerves are vulnerable as theydecussate in the anterior medullary velum, through impact with the tentorial edge. Bilateral lesions are often thought to be unilateral until squint surgery is performed following which the contralateral 4th nerve palsy is often revealed.
3. Vascular lesions are common but aneurysms and tumours are extremely rare. Routine neuroimaging for isolated trochlear palsy is not
• Levator subnucleus is an unpaired caudal midline structure which innervates both levator muscles. Lesions confined to this area will therefore give rise to bilateral ptosis.
• Superior rectus subnuclei are paired: each innervates the respective contralateral superior rectus. A nuclear 3rd nerve palsy will spare the ipsilateral,and affect the contralateral, superior rectus.
• Medial rectus, inferior rectus and inferior oblique subnuclei are paired and innervate their corresponding ipsilateral muscles. Lesions confined to the nuclear complex are relatively uncommon. The most frequent causes are vascular disease, primary tumours and metastases. Involvement of the paired …show more content…
Normal left abduction.
5. Normal left depression.
6. Normal left elevation.
Abnormal head posture avoids diplopia which is vertical, torsional and worse on looking down,contralateral head tilt to the right when trying to inert the eye,To alleviate the inability to depress the eye is adduction,the face is turned to the right and the chin is slightly depressed.
Causes of isolated 4th nerve palsy:
1. Congenital: lesions are common, although symptoms may not develop until decompensation occurs in adult life.Unlike acquired lesions patients are not usually aware of the torsional aspect.
2. Trauma frequently causes bilateral 4th nerve palsy.The long and slender nerves are vulnerable as theydecussate in the anterior medullary velum, through impact with the tentorial edge. Bilateral lesions are often thought to be unilateral until squint surgery is performed following which the contralateral 4th nerve palsy is often revealed.
3. Vascular lesions are common but aneurysms and tumours are extremely rare. Routine neuroimaging for isolated trochlear palsy is not