How to Localize Neurologic Lesion

Question 1

Neurologic deficits can be localized to one of 10 sites:

Answer 1

1. Cerebral cortex
2. Subcortical area
3. Cerebellum
4. Brainstem
5. Spinal cord
6. Plexus (plexopathy)
7. Roots (radiculopathy)
8. Peripheral nerve (peripheral neuropathy)
9. NMJ
10. Muscle (myopathy)

Question 2

Cerebral cortex lesions

Answer 2

Two main deficits:

1. Contralateral motor or sensory deficits
2. Aphasia
   
   1. ​Common when L hemisphere involved
   2. Visual-spatial deficits common when R hemisphere involved

Question 3

Subcortical lesions

Answer 3

1. Internal capsule, cerebral peduncles, thalamus, pons
2. Hemiparesis is usually complete (face, arm, leg) because neurons controlling these structures all merge together subcortically and are very close together

Question 4

Cerebellum lesions

Answer 4

Incoordination, intention tremor, ataxia

Question 5

Brainstem lesions

Answer 5

1. Cranial nerve and spinal cord findings
2. Crossed hemiplegia (deficit on ipsilateral face and contralateral body) b/c corticospinal tract, dorsal columns, and spinothalamic tracts cross but cranial nerves do not

Question 6

Spinal cord lesions

Answer 6

1. With acute injuries, spinal shock may. be present and UMN signs may not be apparent initially.
2. Pt presents with UMN signs (spasticity, increased DTRs, clonus, +Babinski sign), but these signs mayb e present with lesions in brainstem adn cortical/subcortical regions as well
3. Decrease in sensation below a sharp band in the abdomen/trunk. Pinprick felt above this level but not below it. –> pathognomonic for spinal cord disease –> level of lesion corresponds to sensory level

Question 7

Plexopathy

What is the most common cause overall?

What is the most common cause for lumbosacral plexopathy?

Commonly involved plexuses?

Answer 7

1. Deficits (motor and sensory) involve MORE than one nerve
2. Trauma = most common cause overall (esp for brachial plexus)
3. Postsurgical hematoma
4. Erb-Duchenne type –> upper trunk C5-6 and Lumbosacral plexus L5-S3

Question 8

Roots (radiculopathy)

Answer 8

• Pain = key finding***
• Affects a group of muscles supplied by a spinal root (myotome) and a sensory area. supplied by a spinal root. (dermatome)
• Weakness, atrophy, sensory deficits in a dermatomal pattern

Question 9

Peripheral neuropathy

Answer 9

1. Weakness = more prominent distally at outset (as opposed to muscle myopathy) –usually symmetric
2. Dec DTR, numbness, tingling, muscle atrophy, fasciculations
3. Can be due to diabetes, trauma, entrapment, vasculitis
4. Common neuropathies: radila/ulnar/median/musculocutaneous nerves, long thoracic nerve, axillary n., common peroneal n. , femoral n.

Question 10

NMJ

Answer 10

• Fatigability = key finding
• Muscles become weaker with use and recover with rest
• Normal sensation; no atrophy

Question 11

Myopathy

Answer 11

ACQUIRED DISEASE (inherited)

• Symmetric weakness affects proximal muscles more than distal muscles (shoulder/hips)
• Normal reflexes but may diminish late in disease
• NORMAL SENSATION/ NO FASCICULATIONS
• Muscle atrophy may occur late due to disuse (in contrast to rapid atrophy in motor neuron disease)