Localization of Weakness Flashcards
how are deep tendon reflexes affected in UMN vs LMN dysfunction
Normally, deep tendon reflexes do not go to the brain. Deep tendon reflexes go through an interneuron (maybe, or the sensory neuron directly just synapses with the motor neuron that elicits the knee kick or bicep reflex or whatever) and an immediate response is provoked. Brain usually produces top down inhibition. In people with brain injury/babies, inhibition is reduced and thus babinski sign or hyperactive neurons
UMN= brain and spinal cord. –> HIGH DTR
LMN= neuron in the afferent sensory neuron
upper babinski sign is indicative of ___ lesion
UMN
compare and contrast muscle tone, weakness, involuntary movements, reflexes, plantar reflex, and pattern changes in UMN vs LMN weakenss.
weakness is more pronounds in LMN, with fasciculations and reduced reflexes also occuring.
outline the pyramideal or cortical pattern of weakness seen in UMN disease
Upper: extensors weaker than flexors, Lower: flexors are weaker than extensors
compare and contrast cortical, subcortical, brian stem and spinal cord UMN lesiosn and how they manifest in different motor/other findings.
* for subcortical: typically results in hemiparesis, but associated features depend on location. CST is most densely packed in the internal capsule and brainstem. If the internal capsule is affected, ataxia-hemiparesis (incoordination along with weakness of face, arm or leg), or hemiparesis only will be the main motor indicator. YOU TEND TO NOT HAVE THE CORTICAL FINDINGS (ex. Subcortical lesions will not produce language deficits, unliuke if the cortex was lesioned)
* Brainstem: long peripheral nerves are more likely to be damaged because of more SA to be damaged. Cranial N dysfunction is the most common symptom. Can manifest in internuclear ophthalmoplegia because of MLF lesioning: MLF white matter structure that connected the 6th cranial nerve to 3rd CN on the other side. Adjacent to the 6thCN is the PPRF (parapontine reticular formation)– site of where conjugate volitional eye movements are initiated (voluntary eye movement (ex/ look to your left)). The PPRF is closely related to the 6th CN which tells it to move the eye on the same side in a specific direction.
outline how a UMN feature of a brainstem lesion can result in internucelar ophthalmoplegia
Remember; that the 3rd CN gives adduction, and 6th CN gives abduction.
internuclear ophthalmoplegia occurs becuase of MLF lesioning. MLF white matter structure that connects the 6th cranial nerve to 3rd CN on the other side.
Adjacent to the 6thCN is the PPRF (parapontine reticular formation)– site of where conjugate volitional eye movements involving the lateral rectus muscle are initiated (voluntary eye movement (ex/ look to your left)). The PPRF is closely related to the 6th CN which tells it to move the eye on the same side in a specific direction.
PPRF sends a signal to the MLF to tell the contralateral 3rd CN to move the eye on the other side in the same direction
Remember; that the 3rd CN gives adduction, and 6th CN gives abduction. Therefore the PPRF has a specific task to move one eye laterally and the other eye medially at the same time, and it uses the MLF that goes between the midbrain and pons to do so.
The side of the lesion is the side of the abnormal eye movement. Ex/ in image below, the right MLF is lesioned, preventing the right eye from adducting (moving medially), since no signal can go to the 3rdCN in the midbrain.
Remember; that the 3rd CN gives __, and 6th CN gives ___.
Remember; that the 3rd CN gives adduction, and 6th CN gives abduction.The 6th crnaial nerve (abducens) is involved in lateral rectus eye muscle
Stroke facial weakness is an ____ problem, and bells palsy is a ____ neuron problem. Why does it manifest in different weakness profiles (stroke has a facial droop with eyebrow preservation, whereas bells palsy has a whole hemiparesis of one side)
There is some redundancy in the control of the upper quadrants of the face on both side.
If you get an UMN lesion on right side of the brain, the left side of the face will be weak since there is contralateral control of the face generally speaking, but the upper quadrant of the face will have LESS weakness/be more normal because there is some left sided innervation (ipsilateral redundancy)
But if you get a LMN lesion affecting the 7th CN (facial nerve) for example, the common pathway is affected, and so there will be generalized weakness to the whole face.
Outline motor and other sypmtoms of peripheral, motor neuron disease, NMJ, and muscle-locacted LMN lesions.
Compare the antibodies, weakness pattern ,change iwth activity, autonomic featurs, paraneoplastic association and therapies for Lambert Eton and MG syndromes –> which are both ___ disease
both NMJ diseasese (LMN)
Lesions affected the corticospinal tracts can often affect the ___ cranial nerve
Lesions affected the corticospinal tracts can often affect the third cranial nerve Remember that the third cranial nerve (the occipital-motor nerve) goes past the cerebral peduncles
medial longitudinal fasciculus: white matter tract that goes along the brain stem. Important bc it connects ___th cranial nerve and ___rd CN on the other side.
medial longitudinal fasciculus: white matter tract that goes along the brain stem. Important bc it connects 6th cranial nerve and 3rd CN on the other side.
if this white matter tract is severed, can result in internuclear opthalmoplegia
where does crossing over occur in the cortical spino tract
In the pyramids (in the medulla), the corticospinal tracts are also on the more ventral side. At the lower portions of the medulla, there is a crossing over. The sensory decussation is site of cross-over. Before the decussation, the lesion and weakness is contralateral. After the decussation, the lesion and weakness are on the same side.
motor unit
A motor unit, the functional unit of muscle contraction, is a single motor nerve and the associated muscle fibers that are innervated upon stimulation from the nerve. A collection of motor units is referred to as a motor pool
Describe clinical patterns of weakness caused by problems at specific levels of the nervous system
- Pyramidal (internal capsule– anything from the upper motor neuron in the cortex to just above the decussation of the medulla) lesions → ___ hemiparesis
- Brainstem lesion → ____ hemiparesis (ipsilateral face and contralateral body weakness)–> sensory
- Spinal cord → ___ (legs only) or ___ (all limbs)
- Root/radiculi/plexus/nerve → ___paresis
- NMJ → bulbar/respiratory/limbs (__)
- Muscle →__ muscles and symmetric
- Pyramidal (internal capsule– anything from the upper motor neuron in the cortex to just above the decussation of the medulla) lesions → Contralateral hemiparesis (cross over happens at the medullary pyramids– if the lesion is above that, then contralateral presentation will be seen)
- Brainstem lesion → alternating hemiparesis (ipsilateral face and contralateral body weakness)–> sensory
- Spinal cord → paraparesis (legs only) or tetraparesis (all limbs)
- Root/radiculi/plexus/nerve → monoparesis
- NMJ → bulbar/respiratory/limbs (diffuse)
- Muscle →proximal muscles and symmetric
