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Flashcards in Approach to Weakness Deck (61)
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1

origin of peripheral nerves

1) Anterior and lateral gray columns
2) Anterior horn cell axons
3) ventral roots
4) Motor fibers

5) DRG
6) DRG cell axons
7) Dorsal roots
8) sensory fibers

Ventral and dorsal roots join to form mixed spinal nerve

2

Most frequent cause of mononeuropathy

compression injury or entrapment

Different nerves are vulnerable at dif points

Median nerve within carpal tunnel

Ulnar nerve within cubital tunnel

Peroneal nerve across neck of fibula

3

Upper and lower motor neuron tracts

Upper

- cell body in cortex, mainly precentral gyrus
- axon descends via internal capsule into the brainstem where it becomes part of pyramidal tract
- axon crosses over to contralateral side in medulla and enters spinal cord as the corticospinal tract
- synapses with its respective anterior horn cell (this is the LMN)

Lower

- axon leaves spinal cord via ventral root and joins peripheral nerve until it synapses at the NMJ and causes muscle contraction

4

Origin of injuries to UMNs and LMNs

Upper
1) cortex
2) subcortical white matter
3) brainstem
4) spinal cord

Lower
1) anterior horn cell body
2) axon
3) NMJ

5

6 signs of UMN injury

1) No atrophy

2) Increased-spastic tone

3) No fasciculations

4) Weakness with fine, focal movements

5) Increased reflexes

6) Upgoing babinski

6

6 signs of LMN injury

1) Marked atrophy

2) Decreased tone

3) Fasciculations

4) Weakness is distal or in a nerve's distribution

5) Absent or decreased reflexes

6) Absent babinski

7

6 signs of NMJ pathology

1) No atrophy

2) Normal tone

3) No fasciculations

4) weakness in cranial muscles, proximal muscles, fatigable

5) Normal reflexes

6) Absent babinski

8

6 signs of Primary muscle disease

1) Mild atrophy

2) Normal or decreased tone

3) No fasciculations

4) Generally proximal weakness

5) Normal or decreased reflexes

6) Absent babinski

9

Acute hemiparesis

UMN localization (brainstem or above - lesion is contralateral to weakness; upper C spine lesion is ipsilateral to weakness)

Causes:
1) Ischemic CVA
2) hemorrhagic CVA
3) hemorrhage into tumor

Workup:
Immediate HCT or MRI

10

Subacute hemiparesis

UMN localization (brainstem or above - lesion is contralateral to weakness; upper C spine lesion is ipsilateral to weakness)

Causes:
1) Subdural hematoma
2) cerebral abscess
3) malignant neoplasm
4) demyelinating lesion

Workup:
HCT or contrast MRI. Consider c-spine MRI

11

Chronic hemiparesis

UMN localization (brainstem or above - lesion is contralateral to weakness; upper C spine lesion is ipsilateral to weakness)

Causes:
1) Subdural hematoma
2) benign neoplasm

Workup:
HCT or contrast MRI. Consider c-spine MRI

12

Acute paraparesis (both legs weak)

UMN localization usually - thoracic spinal cord or bilateral medial frontal pathology. Look for presence of sensory level. Should have spasticity when subacute or chronic.

UMN causes:
1) spinal trauma
2) epidural hematoma/met/abscess with cord compression
3) transverse myelitis
4) bilateral ACA infarcts
5) sagittal sinus thrombosis
6) acute hyrdocephalus

Workup:
Immediate MRI of the thoracic spine or brain depending on clinical suspicion based on history (back pain) and exam (sensory level)

LMN localization - cauda equina compresion

Causes:
1) Midline lumbar disc herniation
2) Lumbar epidural met

Workup:
Immediate MRI of the lumbosacral spine

13

Subacute to chronic paraparesis

UMN localization usually - thoracic spinal cord or bilateral medial frontal pathology. Look for presence of sensory level. Should have spasticity when subacute or chronic.

Causes:
1) B12 deficiency
2) intraspinal tumor
3) slow compression by degenerative disc disease
4) MS
5) hereditary diseases
6) tabes dorsalis

Workup:
MRI of spine, serum B12, RPR

14

Acute quadriparesis

UMN - above C4

Causes:
1) cervical cord compression - tumor/abscess/hematoma
2) basilar artery occlusion
3) global anoxic injury

workup:
Consider immediate intubation if respiratory paralysis present. If comatose, HCT. If awake, MRI brain with or without c-spine

LMN

Causes:
1) Severe Guillain-Barre
2) Other acute neuropathies

Workup:
Possible intubation, EMG/NCS, LP

Muscle disease

Causes:
1) Periodic paralysis (rare)

Workup:
Serum K

15

Subacute Quadriparesis

LMN
Causes: GBS or other acute neuropathies

Muscle disease
Causes:
1) Critical illness myopathy
2) statins

Workup: CPK, EMG, muscle bx

16

Chronic quadriparesis

UMN - above C4
Causes:
1) Slowly growing tumor (meningioma) with cervical cord compression
2) B12
3) Tabes

Workup: MRI brain and c-spine, B12, RPR

LMN
Causes:
1) ALS (will have UMN signs too)

Workup: EMG

17

Acute monorparesis (1 limb weak)

UMN
Causes:
1) Diabetic distal cortical infarct

Workup: MRI brain

LMN
Causes:
1) Diabetic or vasculitic (polyarteritis, Wegeners) mononeuritis

Workup: EMG, NCS, Hemoglobin A1C, pANCA, cANCA, ESR

18

Subacute monoparesis

LMN
Causes:
1) myeloma
2) amyloidosis
3) leprosy
4) diabetic or vasculitic

Workup: SPEP, serum light chains, EMG, NCS, A1C, ANCAs, ESR

19

Acute-subacute distal weakness

LMN
Causes:
1) GBS
2) chemo
3) isoniazid

Workup: EMG, NCS

20

Chronic distal weakness

LMN
Causes:
1) Diabetes
2) Alcoholism
3) hereditary neuropathy (charcot-marie tooth)
4) uremia

Workup: EMG, NCS

21

Subacute-chronic proximal weakness (shoulders and hips)

Muscle disease
Causes:
1) Muscular dystrophies
2) Myotonic dystrophy
3) polymyositis
4) Dermatomyositis
5) inclusion body myositis
6) endocrine myopathies
7) critical illness

Workup: CPK, EMG, Muscle bx

22

Acute anterior horn cell diseases (motor neuronopathies)

Poliomyositis

23

Poliomyositis

Begins as an aseptic lymphocytic meningitis with fever, HA, stiff neck followed in 1 in 1000 by asymmetric lower motor neuron weakness

Tx = prevention with vaccine

24

Chronic anterior horn cell diseases

ALS

25

ALS

Begins insidiously with distal muscle weakness with fasciculations

Atrophy is seen

This is also a disease of the corticospinal tract so both UMN and LMN signs are seen

All patients eventually develop diaphragmatic and pharyngeal weakness and die

Tx: Riluzole prolongs survival minimally

PEG should be considered before VC is less than 50%

26

Congenital causes of anterior horn cell disease

Spinal muscular atrophy

27

Spinal muscular atrophy

In the most severe form (type 1 - werdnig hoffman), presents with neonatal hypotonia

28

Different neuropathy origins

1) Diabetes
2) Nutritional deficiency
3) B12
4) GBS (acute inflammatory demyelinating polyneuropathy)
5) Chronic inflam demyelin polyneuro
6) Chemo agents
7) Antibiotics
8) Nonmedicinal toxins
9) Infections
10) Neoplasms
11) Systemic diseases
12) Hereditary diseases

29

Diabetic neuropathy

Mononeuritis multiplex
Distal, symmetrical polyneuropathy
Cranial neuropathy

Most commonly causes a slowly progressive sensory more than motor DSPN which increases the risk of diabetic foot ulcers

Always look for it on PE of diabetic patient

30

neuropathy secondary to nutritional deficiency

DSPN

Usually seen in alcoholics and other chronically malnourished patients

Important vitamins are B1, B6 and Folate