Brainstem lesions from module Flashcards
Unilateral Lesion of the Trigeminal Nerve
results in:
- Anesthesia and loss of general sensations in the trigeminal dermatomes
- Loss of jaw jerk reflex
- Atrophy of the muscles of mastication
- Loss of ipsilateral and consensual corneal reflex
Alternating Analgesia
Brainstem lesions in the upper medulla may destroy the primary fibers in the descending tract of V and the secondary fibers in the spinal lemniscus.
ipsilateral hemianalgesia of the face, and contralateral hemianalgesia of the body.
Alternating Trigeminal Hemiplegia i
- result of a unilateral destruction of
- the trigeminal nerve amd corticospinal tract in the pons
- results in ipsilateral trigeminal anesthesia and paralysis, and contralateral spastic hemiplegia
Tic Douloureux
- Trigeminal Neuralgia
- cutaneous region on the head called a trigger zone may initiate abnormal “epileptic-like” discharges from the subnucleus caudalis.
- intractable, lacerating facial pain following affected division of V
- may be treated with anticonvulsant medication
- Unilateral lesion of the Cochlear nerve
- Unilateral lesion of the central auditory pathway
- Lesions of the Primary Auditory Cortex
- Auditory Agnosia
- Unilateral lesion of the Cochlear nerve results in ipsilateral complete deafness.
- Unilateral lesion of the central auditory pathway results in a bilateral diminution of hearing which is more prominent in the contralateral ear. These structures include the lateral lemniscus, inferior colliculus and brachium, and the medial geniculate body.
- Lesions of the Primary Auditory Cortex result in a difficulty in localizing sounds and tone discrimination. It does not result in hearing deficits.
- Auditory Agnosia. Lesions in the auditory association (POT) cortex may result in an auditory agnosia characterized by an inability to comprehend auditory information. Spoken and written language as well as other sensory modalities may remain in
Argyll Robertson pupil
- pupil will accommodate but not react.
- indicates a lesion in the pretectum
- light reflex does not elicit pupillary constriction, but bringing an object towards the eyes will cause it to constrict, lens will thicken, and vision converges on the object.
Holmes Adie Pupil
- Tonic (Adie) pupil
- benign condition, may be due to a lesion of the ciliary ganglion.
- may be initially confused with an Argyll- Robertson pupil because similar light reflexes
- distinguished by different reactions to accommodation.
- Initially: tonic pupil does not appear to react to convergence.
- If convergence is maintained for several seconds pupil will slowly constrict; affected pupil may be smaller than the normal pupil.
- Eye drops containing parasympathomimetic agents such as methacholine or pilocarpine will constrict the tonic pupil, but will have no effect on the normal pupil.
- Tonic pupil is more common in young adult females.
normal scotoma
blindspot at the optic disc
lesions of the visual system are always described in
terms of their visual field deficits.
Pituitary tumors frequently impinge upon the chiasm, which results
Pituitary tumors frequently impinge upon the chiasm, which results in a characteristic pattern of field blindness (bitemporal hemianopia).
a tumor or infarction in the posterior temporal lobe.
- Contralateral superior quadrantanopia.
- Unilateral lesions of the loop of Meyer usually result in this homonymous deficit.
- It may be caused by a tumor or infarction in the posterior temporal lobe. Below is an example of a left superior quadrantanopia, which would indicate a lesion of the right loop of Meyer.
Incongruent contralateral homonymous hemianopia with macular sparing
usually indicative of a unilateral lesion of the visual cortex.
It may be due to obstruction of the posterior cerebral artery.
Lesions of the visual cortex are usually incongruous (asymmetrical) whereas lesions of the LGB or optic radiations are congruous in their visual field deficits. Below is an example of a left incongruent homonymous hemianopia with macular sparing, which would indicate a lesion of the right primary visual cortex.
