Weakness Flashcards
Lower motor neuron signs, including focal weakness and prominent muscle atrophy, decreased muscle stretch reflexes and tone, and fasciculations, may occur from lesions occurring anywhere…
…along the length of the spinal cord or brainstem lower motor neurons.
Presentation of a lesion in a single peripheral nerve?
LMN signs as well as sensory impairment confined to its anatomical territory +/- painful paresthesia/dysesthesia
Presentation of most cases of peripheral neuropathy (aka polyneuropathy)?
Distal limb LMN signs and sensory (stocking and glove) loss, typically beginning in the lower limbs.
Presentation of a lesion of the brachial or lumbosacral plexus?
LMN signs and sensory deficit according to the anatomical territory of the trunk, division, or cord of the plexus involved
Presentation of a radiculopathy?
Neck or back pain which may radiate into a limb or the trunk in a dermatomal distribution, along which tingling or numbness may also occur, LMN signs in muscles innervated by the involved spinal nerve root
Presentation of an anterior horn cell lesion?
May cause weakness in a distal or proximal segment of a limb, eventually becoming more widespread and bilateral with prominent fasciculations in ALS; ALS may also affect the brain stem lower motor neurons involved with speaking, chewing, or swallowing
In general, pain may often accompany lesions of roots, plexus, or nerves, but not lesions of ___.
Anterior horn cells
Lesions leading to UMN signs, including more diffuse weakness with relatively less muscle atrophy, hyperreflexia, spasticity, and Babinski signs, often occur in limbs on one side of the body; responsible lesions may occur anywhere…
…along the extent of the corticospinal tract from the motor cortex down to the spinal cord.
Presentation of an ipsilateral cervical spinal cord lesion?
Hemiplegia, neck and radicular pain and LMN signs if cervical root is also involved at the level of the lesion; there may be ipsilateral sensory deficits for position sense and vibration (dorsal columns) and contralateral sensory deficits for pain and temperature (STT) up to a dermatomal level
Presentation of a brain stem UMN lesion?
Hemiplegia, facial weakness, dysarthria, dysphagia
Presentation of a subcortical lesion in the internal capsule or corona radiata?
Hemiplegia with relatively equal weakness in the contralateral lower face and upper and lower limbs, since the descending motor fibers are compacted closely in this area
Presentation of a cortical lesion?
Hemiplegia; weakness may be unequal between the affected upper and lower limbs -> hemiplegia with the leg weaker than the face and arm is caused by a lesion with a lesion in the more medial (parasagittal) portion of the contralateral motor cortex vs. hemiplegia with the face and arm weaker than the leg with a lesion in the more lateral portion of the contralateral motor cortex
+/- sensory deficits in the lower limb if sensory cortex involved
+/- aphasia (dominant hemisphere involvement)
+/- contralateral visual field deficits
Where is motor function controlled in the cortex?
Precentral gyrus
Where is sensory function controlled in the cortex?
Post-central gyrus
Describe the general homunculus of the cortex from medial to lateral.
[Genitals]->Foot->Leg->Trunk->Arm->Hand->Face->Tongue
Ischemic infarction of the ___ artery or one of its branches commonly leads to hemiplegia with the leg weaker than the face and arm.
ACA
Ischemic infarction of the ___ artery or one of its branches leads to hemiplegia with the face and arm weaker than the leg.
MCA
Which artery does not perfuse the motor cortex?
PCA
The time it takes for UMN weakness to develop is another clue to its etiology. Compare the causes of sudden onset vs. gradual onset of hemiplegia.
Sudden: cerebrovascular lesion, trauma
Gradual: tumor, degenerative disease
What does “bulbar” refer to and what cranial nerves control “bulbar” functions?
Lower brain stem, where lesions of the 5th, 7th, 9th, 10th, or 12th CNs can cause weakness of chewing, speaking or swallowing
Presentation of a bulbar palsy?
LMN signs -> atrophy and fasciculations of the muscles of the face, jaws, palate, or tongue
Presentation of a pseudobulbar palsy?
Weakness of chewing, speaking, or swallowing caused by lesions in the UMNs (corticobulbar tract); signs include a hyperactive jaw jerk in the absence of atrophy or fasciculations of the weakened muscles
DDx in patients with weakness who lack LMN or UMN signs?
Disorder or muscle or the NMJ
- Muscle disease, expect proximal limb weakness, reflexes preserved initially with disappearance s/p significant atrophy
- NMJ disorders like MG, expect variable weakness and fatigue of the limbs, often accompanied by ptosis, diplopia, dysarthria, dysphagia, or dyspnea
Patients who report weakness, may actually have slowness or clumsiness, which may be due to problems with what systems?
Extrapyramidal (basal ganglia in particular) or cerebellar systems
General functions of the basal ganglia?
Postural control
Muscle tone
More “automatic” types of movements
General functions of the cerebellum and its connections?
Balance, smoothness, and coordination of movement
