Weakness

Question 1

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…

Answer 1

…along the length of the spinal cord or brainstem lower motor neurons.

Question 2

Presentation of a lesion in a single peripheral nerve?

Answer 2

LMN signs as well as sensory impairment confined to its anatomical territory +/- painful paresthesia/dysesthesia

Question 3

Presentation of most cases of peripheral neuropathy (aka polyneuropathy)?

Answer 3

Distal limb LMN signs and sensory (stocking and glove) loss, typically beginning in the lower limbs.

Question 4

Presentation of a lesion of the brachial or lumbosacral plexus?

Answer 4

LMN signs and sensory deficit according to the anatomical territory of the trunk, division, or cord of the plexus involved

Question 5

Presentation of a radiculopathy?

Answer 5

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

Question 6

Presentation of an anterior horn cell lesion?

Answer 6

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

Question 7

In general, pain may often accompany lesions of roots, plexus, or nerves, but not lesions of ___.

Answer 7

Anterior horn cells

Question 8

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…

Answer 8

…along the extent of the corticospinal tract from the motor cortex down to the spinal cord.

Question 9

Presentation of an ipsilateral cervical spinal cord lesion?

Answer 9

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

Question 10

Presentation of a brain stem UMN lesion?

Answer 10

Hemiplegia, facial weakness, dysarthria, dysphagia

Question 11

Presentation of a subcortical lesion in the internal capsule or corona radiata?

Answer 11

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

Question 12

Presentation of a cortical lesion?

Answer 12

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

Question 13

Where is motor function controlled in the cortex?

Answer 13

Precentral gyrus

Question 14

Where is sensory function controlled in the cortex?

Answer 14

Post-central gyrus

Question 15

Describe the general homunculus of the cortex from medial to lateral.

Answer 15

[Genitals]->Foot->Leg->Trunk->Arm->Hand->Face->Tongue

Question 16

Ischemic infarction of the ___ artery or one of its branches commonly leads to hemiplegia with the leg weaker than the face and arm.

Answer 16

ACA

Question 17

Ischemic infarction of the ___ artery or one of its branches leads to hemiplegia with the face and arm weaker than the leg.

Answer 17

MCA

Question 18

Which artery does not perfuse the motor cortex?

Answer 18

PCA

Question 19

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.

Answer 19

Sudden: cerebrovascular lesion, trauma

Gradual: tumor, degenerative disease

Question 20

What does “bulbar” refer to and what cranial nerves control “bulbar” functions?

Answer 20

Lower brain stem, where lesions of the 5th, 7th, 9th, 10th, or 12th CNs can cause weakness of chewing, speaking or swallowing

Question 21

Presentation of a bulbar palsy?

Answer 21

LMN signs -> atrophy and fasciculations of the muscles of the face, jaws, palate, or tongue

Question 22

Presentation of a pseudobulbar palsy?

Answer 22

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

Question 23

DDx in patients with weakness who lack LMN or UMN signs?

Answer 23

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

Question 24

Patients who report weakness, may actually have slowness or clumsiness, which may be due to problems with what systems?

Answer 24

Extrapyramidal (basal ganglia in particular) or cerebellar systems

Question 25

General functions of the basal ganglia?

Answer 25

Postural control
Muscle tone
More “automatic” types of movements

Question 26

General functions of the cerebellum and its connections?

Answer 26

Balance, smoothness, and coordination of movement