The Approach to Weakness

Question 1

Describe the pattern of weakness seen with primary muscle disorders.

Answer 1

predominantly weakness in proximal muscles, in a symmetric fashion

distal muscles are affected later or not as severely

neck flexors and extensors (which are not affected in most nerve or break lesions) may be weak in a muscle disorder

Question 2

What are some associated signs and symptoms that may tip you off to a primary muscle disorder?

Answer 2

muscle pain (if the disorder is inflammatory)

by their very nature, primary muscle disorders shouldn’t cause numbness of tingling

reflexes are preserved unless the process is so severe that the muscles are nearly paralyzed.

Question 3

What lab finding will suggest a primary muscle disorder?

Answer 3

elevated serum creatine kinase level

Question 4

Do most NMJ problems affect distal or proximal muscles?

Answer 4

mostly proximal limb muscles

Question 5

The characteristic feature of NMJ disorders is not the pattern of weakness, but what?

Answer 5

the fluctuation - NMJ disorder weakness can vary from hour to hour (may be worse after using the muscles or toward the end of the day, or may improve with use/rest)

Question 6

True or false: sensory signs and symptoms are common with NMJ disorders.

Answer 6

false

Question 7

What is the pattern of weakness in peripheral nerve disorders

Answer 7

It depends on if there is only one nerve affected (a mononeuropathy) or multiple nerves affected (a polyneuropathy)

in mono - only one muscle will show weakness
in poly - multiple muscles (and can be far away from each other) will show weakness; usually distal>proximal (because longer nerves are affected first)

Question 8

What are some associated signs/symptoms that suggest a peripheral nerve issue?

Answer 8

pain, numbness, tingling, depressed or absent reflexes

Question 9

What do we call a problem involving nerve roots?

Answer 9

radiculopathy (and polyradiculopathy if there is dysfunction of multiple nerve roots)

Question 10

What are the associated signs and symptoms that suggest a radiculopathy?

Answer 10

tingling and pain radiating out from the back or neck

Question 11

In general terms, what is the pattern of weakness with a plexus problem?

Answer 11

weakness that doesn’t conform to a peripheral nerve or nerve root pattern

Question 12

Spinal cord disorders cause weakness in what two ways?

Answer 12

1. The anterior horn cells located at the level of the lesion are affected, leading to weakness of the muscles innervated by the nerve root at that level
2. weakness below the level of the lesion due to interruption of the descending corticospinal tracts in an upper motor neuron pattern

Question 13

What are some associated signs and symptoms of a spinal cord disorder?

Answer 13

loss of sensation below a particular dermatomal level

DTRs below the lesion will be increased

maybe babinski sign

bladder and bowel incontinence depending on level

Question 14

What is the pattern of weakness caused by disorders of the cerebral hemispheres?

Answer 14

UMN pattern of weakness of the contralateral body (location of weakness depending on the location of the lesion along the homunculus; weakness in face, arm and leg suggests internal capsule)

Question 15

Weakness in the ipsilateral face and contralateral arm/leg (crossed signs) suggests a lesion where?

Answer 15

base of the pons (because the descending motor fibers to the face have already crossed at that level, but those for the body have not)