Cranial Nerve Lesions
Trigeminal Nerve Lesion (CN V): A lesion to the trigeminal nerve will result in altered x on the side of the face ipsilateral to the lesioned nerve. o One example is Trigeminal neuralgia. This is a condition characterized by brief attacks of excruciating pain, usually less than a minute in duration, which occur in the distribution of x of the divisions of CN V. Between attacks there are no significant sensory abnormalities. Most cases appear to be caused by x of the trigeminal nerve.
Trigeminal Nerve Lesion (CN V): A lesion to the trigeminal nerve will result in altered sensation on the side of the face ipsilateral to the lesioned nerve. o One example is Trigeminal neuralgia. This is a condition characterized by brief attacks of excruciating pain, usually less than a minute in duration, which occur in the distribution of one of the divisions of CN V. Between attacks there are no significant sensory abnormalities. Most cases appear to be caused by compression of the trigeminal nerve.
Trochlear Nerve Lesion (CN IV): The eye ipsilateral to the lesioned nerve will be affected in the following ways: There will be weakness in attempts to move the affected eye xward (paralysis of the superior oblique) such as is necessary when reading or walking downstairs. There may be x vision, with these activities. Additionally the superior oblique causes intorsion or medial rotation of the eye. When paralyzed, the eye may be in a position of xtorsion or x rotation at rest. To align the two eyes and avoid diplopia, the patient may x away from the affected side to effectively "Intort" the paralyzed eye.
Trochlear Nerve Lesion (CN IV): The eye ipsilateral to the lesioned nerve will be affected in the following ways: There will be weakness in attempts to move the affected eye downward (paralysis of the superior oblique) such as is necessary when reading or walking downstairs. There may be diplopia, double vision, with these activities. Additionally the superior oblique causes intorsion or medial rotation of the eye. When paralyzed, the eye may be in a position of extorsion or lateral rotation at rest. To align the two eyes and avoid diplopia, the patient may tilt their head away from the affected side to effectively "Intort" the paralyzed eye.
Abducens Nerve Lesion (CN VI): The eye ipsilateral to the lesioned nerve will be affected in the following ways: The affected eye will deviate xlly due to paralysis of the lateral rectus and unopposed action of the medial rectus. This condition or posture of the eye is referred to as x. Patients may be able to move the affected eye back to a mid-position from an adducted position due to x of the medial rectus. x (horizontal gaze) will also be affected in this patient. More detail on this specific deficit will come in the "Gaze" lecture.
Abducens Nerve Lesion (CN VI): The eye ipsilateral to the lesioned nerve will be affected in the following ways: The affected eye will deviate medially due to paralysis of the lateral rectus and unopposed action of the medial rectus. This condition or posture of the eye is referred to as medial strabismus. Patients may be able to move the affected eye back to a mid-position from an adducted position due to relaxation of the medial rectus. Lateral (horizontal gaze) will also be affected in this patient. More detail on this specific deficit will come in the "Gaze" lecture.
Facial Nerve Lesion (CN VII): Damage to the facial nerve will result in paralysis of the muscles of facial expression on the xlateral half of the face.
Facial Nerve Lesion (CN VII): Damage to the facial nerve will result in paralysis of the muscles of facial expression on the ipsilateral half of the face.
Hypoglossal Nerve Lesion (CN XII): A lesion to this nerve will cause paralysis of tongue musculature xlateral to the lesioned nerve. Because the fibers in this nerve are x motor neurons, there may also be x of ipsilateral tongue musculature. Paralysis of tongue musculature can be assessed by asking the patient to protrude (stick out) his/her tongue. When musculature is intact bilaterally, the tongue protrudes straight. When one side is paralyzed, muscles on the contralateral side are unopposed and their unopposed action causes the tongue to deviate toward the side where the muscles are weak/paralyzed, which is also toward the side where the nerve is lesioned.
Hypoglossal Nerve Lesion (CN XII): A lesion to this nerve will cause paralysis of tongue musculature ipsilateral to the lesioned nerve. Because the fibers in this nerve are lower motor neurons, there may also be atrophy of ipsilateral tongue musculature. Paralysis of tongue musculature can be assessed by asking the patient to protrude (stick out) his/her tongue. When musculature is intact bilaterally, the tongue protrudes straight. When one side is paralyzed, muscles on the contralateral side are unopposed and their unopposed action causes the tongue to deviate toward the side where the muscles are weak/paralyzed, which is also toward the side where the nerve is lesioned.To test the function of the nerve, a patient is asked to stick their tongue straight out. If there is a loss of innervation to one side, the tongue will curve toward the affected side, due to unopposed action of the opposite genioglossus muscle. If this is the result of a lower motor neuron lesion, the tongue will be curved toward the damaged side, combined with the presence of fasciculations or atrophy. However, if the deficit is caused by an upper motor neuron lesion, the tongue will be curved away from the side of the cortical damage, without the presence of fasciculations or atrophy.[3]
Oculomotor Nerve Lesion (CN III): The eye ipsilateral to the lesioned nerve will be affected in the following ways: The affected eye will deviate Xlly due to paralysis of the medial rectus and unopposed action of the lateral rectus. This condition or posture of the eye is referred to as X (i.e. a misalignment of the eyes where one eye deviates laterally from the mid-position). The result is X or double vision since the two eyes are now essentially "looking in different directions". The patient will be unable to move the eye Xlly (paralyzed X rectus) and vertical i.e. superior and inferior motions will be impaired (paralyzed superior and inferior rectus muscles). Ptosis or drooping of the eyelid on the X side. X or dilation of the pupil on the affected side. The pupil on this side will also not Xt in response to light. o Of clinical note, the Xganglionic fibers in CN III control constriction of the pupil. These fibers are the most X within CN III and thus are often the first to be compressed with external pressure on this nerve. Therefore one of the first clinical findings with pressure on CN III may be a x pupil which is unresponsive to x.
Oculomotor Nerve Lesion (CN III): The eye ipsilateral to the lesioned nerve will be affected in the following ways: The affected eye will deviate laterally due to paralysis of the medial rectus and unopposed action of the lateral rectus. This condition or posture of the eye is referred to as lateral strabismus (i.e. a misalignment of the eyes where one eye deviates laterally from the mid-position). The result is diplopia or double vision since the two eyes are now essentially "looking in different directions". The patient will be unable to move the eye medially (paralyzed medial rectus) and vertical i.e. superior and inferior motions will be impaired (paralyzed superior and inferior rectus muscles). Ptosis or drooping of the eyelid on the affected side. Mydriasis or dilation of the pupil on the affected side. The pupil on this side will also not constrict in response to light. o Of clinical note, the preganglionic fibers in CN III control constriction of the pupil. These fibers are the most superficial within CN III and thus are often the first to be compressed with external pressure on this nerve. Therefore one of the first clinical findings with pressure on CN III may be a dilated pupil which is unresponsive to light.
Optic Nerve Lesion (CN II): A complete lesion of the optic nerve will cause X. Incomplete lesions, e.g. in Demyelinating diseases like Multiple Sclerosis, will cause X vision. You will later learn about other visual field deficits which relate to lesions along the central visual pathway.
Optic Nerve Lesion (CN II): A complete lesion of the optic nerve will cause monocular blindness. Incomplete lesions, e.g. in Demyelinating diseases like Multiple Sclerosis, will cause blurry vision. You will later learn about other visual field deficits which relate to lesions along the central visual pathway.
