Chapter 5: Approach to Weakness

Question 1

Primary Muscle Weakness

Answer 1

Proximal>Distal
May cause muscle pain. 
No sensory signs. 
Reflexes preserved. 
Elevated creatine kinase.
Myopathic pattern on EMG

Question 2

Neuromuscular Junction Disorders

Answer 2

Proximal Extremity
Fluctuating weakness (over the day, improves with rest, may improve with exercise)
No sensory signs
e.g. Myasthenia gravis, Lambert-Eaton myasthenic syndrome
Can affect extraocular and bulbar muscles

Question 3

Peripheral Nerve Disorders

Answer 3

Mononeuropathies
Polyneuropathy (all peripheral nerves affected diffusely)
Distal muscles (longest nerves)
Sensory symptoms+ (numbness, tingling, pain)

Question 4

Mononeuropathy multiplex

Answer 4

Dysfunction of multiple peripheral nerves in succession

Characteristically associated with pain

Question 5

Peripheral Nerve Disorder examples

Answer 5

Mononeuropathies most comnon due to entrapment (carpal tunnel)
Mononeuropathy multiplex associated with systemic vasculitis and other metabolic or rheumatologic diseases.
Demyelinating polyneuropathies: hereditary (charco-marie-tooth) or aqquired (Guillain-Barre)

Question 6

Nerve roots and muscle movements

Answer 6

?

Question 7

Nerve Root Disorders

Answer 7

Radiculopathies
Tingling or pain, radiating out from the neck or back
Weakness in muscles from the nerve root
Reflex may be depressed or absent
EMG/NCS can confirm nerve roots as the cause
Single radiculopathies: MRI for structural (varicella-zoster virus)
Polyradiculopathies: LP for infectious or inflammatory conditions

Question 8

Plexus Disorders

Answer 8

Should be suspected where multiple weak muscles not explained by a nerve root or peripheral nerve pattern
Sensory signs or reflex loss may be present
Confirmed by EMG/NCS

Question 9

Diabetic Amyotrophy

Answer 9

Lumbosacral plexopathy

Question 10

Spinal Cord Disorders

Answer 10

Can affect anterior horns, corticospinal tracts, spinothalamic, etc.
Will effect weakness below the lesion and at the lesion, sensory loss below the lesion.
MRI to rule out structural etiologies
LP for infectious, inflammatory, or neo-plastic possibilities.

Question 11

Spinal Cord Disorders examples

Answer 11

Inflammatory (transverse myelitis)
AML (corticospinal tracts and anterior horn cells)
Infarction
Compression
Misc.

Question 12

Lower Motor vs. Upper Motor neurons cause fasciculations

Answer 12

LMN disease

Question 13

UMN lesions can lead to

Answer 13

Spasticity, hyperactive reflexes, Babinski sign, incontinence

Question 14

Disorders of the Cerebral Hemispheres and Brainstem

Answer 14

The body part affected describes where the lesion is:
Leg (parasagittal)
Face and Arm (Lateral hemisphere)
Deep hemispheric (internal capsule, affects farm, arm, and leg)
Base of pons (weakness of ipsilateral face and contralateral arm and leg) (crossed signs)
Look for contralateral deficits
Frequently associated with Cognitive signs (aphasia/apraxia on Left. Neglect/visuospatial dysfunction on right. CN problems in brainstem)
Image the brain

Question 15

DDx for Disorders of brain and brainstem

Answer 15

Stroke, demyelinating disease, traumatic injury, brain tumor, infection