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Neurology > Approach to Weakness > Flashcards

Approach to Weakness Flashcards

1
Q

origin of peripheral nerves

A

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

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2
Q

Most frequent cause of mononeuropathy

A

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

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3
Q

Upper and lower motor neuron tracts

A

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
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4
Q

Origin of injuries to UMNs and LMNs

A

Upper

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

Lower

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

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5
Q

6 signs of UMN injury

A

1) No atrophy
2) Increased-spastic tone
3) No fasciculations
4) Weakness with fine, focal movements
5) Increased reflexes
6) Upgoing babinski

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6
Q

6 signs of LMN injury

A

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

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7
Q

6 signs of NMJ pathology

A

1) No atrophy
2) Normal tone
3) No fasciculations
4) weakness in cranial muscles, proximal muscles, fatigable
5) Normal reflexes
6) Absent babinski

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8
Q

6 signs of Primary muscle disease

A

1) Mild atrophy
2) Normal or decreased tone
3) No fasciculations
4) Generally proximal weakness
5) Normal or decreased reflexes
6) Absent babinski

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9
Q

Acute hemiparesis

A

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

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10
Q

Subacute hemiparesis

A

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

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11
Q

Chronic hemiparesis

A

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

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12
Q

Acute paraparesis (both legs weak)

A

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

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13
Q

Subacute to chronic paraparesis

A

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

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14
Q

Acute quadriparesis

A

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

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15
Q

Subacute Quadriparesis

A

LMN
Causes: GBS or other acute neuropathies

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

Workup: CPK, EMG, muscle bx

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16
Q

Chronic quadriparesis

A 
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

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17
Q

Acute monorparesis (1 limb weak)

A

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

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18
Q

Subacute monoparesis

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

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

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19
Q

Acute-subacute distal weakness

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

Workup: EMG, NCS

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20
Q

Chronic distal weakness

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

Workup: EMG, NCS

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21
Q

Subacute-chronic proximal weakness (shoulders and hips)

A 
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

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22
Q

Acute anterior horn cell diseases (motor neuronopathies)

A

Poliomyositis

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23
Q

Poliomyositis

A

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

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24
Q

Chronic anterior horn cell diseases

A

ALS

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25
Q

ALS

A

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
Q

Congenital causes of anterior horn cell disease

A

Spinal muscular atrophy

27
Q

Spinal muscular atrophy

A

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

28
Q

Different neuropathy origins

A

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
Q

Diabetic neuropathy

A

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
Q

neuropathy secondary to nutritional deficiency

A

DSPN

Usually seen in alcoholics and other chronically malnourished patients

Important vitamins are B1, B6 and Folate

31
Q

B12 deficiency neuropathy

A

DSPN

Usually masked by the UMN signs from spinal cord disease

32
Q

GBS neuropathy

A

Demyelinating polyneuropathy

Causes progressive weakness and pain that usually begins in the legs. Weakness must peak by 4 weeks.

CSF shows cytoalbumniologic dissociation (high protein, no cells).

Can progress to involve diaphragm

If nonambulatory, treatment is either IVIG or plasmapheresis. Most common cause of disability in young people.

33
Q

Chronic inflammatory demyelinating polyneuropathy

A

Demyelinating polyneuropathy

Similar to GBS but weakness continues to progress after 4 weeks. CSF may have elevated protein

Treatment is with steroids

34
Q

Chemo neuropathy

A

DSPN

Usually dose related. May be sensorimotor (pain and weakness) or just sensory

Most common agents are vincristine, cisplatin, and taxol

35
Q

ABx neuropathy

A

DSPN

Usually dose related. May be sensorimotor (pain and weakness) or just sensory

Most common agents are isoniazid (without B6), metronidazole and nucleoside antagonists

36
Q

Nonmedical toxin induced neuropathy

A

DSPN, MM

Lead in adults causes mononeuritis multiplex, especially involving the radial nerve causing a wrist drop

Diphtheria toxin mimics GBS

Must always have high index of suspicion to recognize these diagnoses

37
Q

Infection-induced neuropathy

A

DSPN, MM, dermatomal, CN

HIV, Lyme, leprosy can cause various types of neuropathies

Leprosy involves cooler areas (nose, ears)

VZV (shingles) can cause a dermatomal sensory loss

HIV neuropathy may be seen in patients even with good CD4 counts

38
Q

Neoplasm-associated neuropathy

A

MM, DSPN

Multiple myeloma and MGUS are the most frequent and SPEP should be performed on all patients with no clear cause of their neuropathy

Paraneoplastic sensory neuropathy can be seen with small cell lung cancer

39
Q

Systemic disease-associated neuropathy

A

DSPN

Seen in critical illness, uremia, hepatic disease, hypothyroidism, porphyria

Variably reversible with correction of systemic process

40
Q

Hereditary disease-associated neuropathy

A

DSPN, MM

Most common is Charcot-Marie-Tooth - autosomal dominant on chrom 17. Causes slowly progressive demyelinating neuropathy which presents in 20s.

Hereditary neuropathy with liability to pressure palsies (HNPP) causes easy damage to nerves at vulnerable points so that even an insignificant injury can cause a mononeuropathy

Associated pes cavus is seen. Other rare forms of CMT exist.

41
Q

Myasthenia Gravis patho

A

Autoimmune caused by antibodies against ACh receptor on muscles

42
Q

MG clinical features

A

Peaks in women in 20s-30s. Later in men

Cardinal feature is fatigability. The weakness increases with activity and improves with rest.

Generally involves cranial muscles causing ptosis, diplopia, dysphagia, dysarthria and difficulty chewing tough foods

In 85% prox limbs are involved as well.

Aminoglycosides and skeletal muscle depolarizing agents exacerbate the weakness

43
Q

Dx of MG

A

1) Edrophonium test after fatigue is reached
2) ACh receptor antibody serologies in 50% of ocular and 90% of generalized
3) On EMG the amplitude of the muscle response decreases with repetitive stimulation
4) CT of the chest may demonstrate thymoma

44
Q

Tx of MG

A

Symptomatic therapy achieved with cholinesterase inhibitors (pyridostigmine), which increases the available ACh

The underlying disease is treated with thymectomy and immunosuppression using steroids or steroid sparing agents like azathioprine and cyclosporine

Myasthenic crisis involving respiratory muscles treated with IVIG or plasmapheresis

45
Q

Botulism

A

Another NMJ disease

Botulism toxin prevents release of ACh vesicles from presynaptic neuron

Acute intox causes descending paralysis with diplopia, dysarthria, dysphagia, respiratory difficulty and limb weakness

Dx:
Difficult. Involves finding evidence of the toxin in stool or vomitus

Tx: equine antitoxin as well as good supportive care

46
Q

Lambert-Eaton myasthenic syndrome

A

Paraneoplastic disease resulting from antibodies to voltage-gated calcium channels produced by small cell lung cancer

Prox muscle weakness of the legs with ptosis and diplopia is seen. Unlike MG, reflexes are depressed and autonomic dysfunction are seen (dry mouth, impotence)

Can test for the antibody. Also, on repetitive nerve stimulation, the motor amplitude INCREASES as more calcium is mobilized into presynaptic terminal

Tx = tx of underlying lung cancer is standard treatment

47
Q

Types of muscle diseases (myopathies)

A

“Eat Dip”

Endocrine myopathies
Adult onset muscular dystrophies
Toxic myopathies

Dermatomyositis
Inclusion body myositis
Polymyositis

48
Q

Polymyositis

A

presumed autoimmune attack against muscle with lymphocytic infiltration. Can be primary idiopathic or associated with a collagen vascular disease

Insidiously progressive generally over weeks to months. Like most myopathies, prox muscles are involved earliest with difficulty arising from a seated position or reaching up to retrieve an object. 25% have dysphagia. 30% develop ECG changes. 10% have pain. females more than men.

Dx: CPK is generally elevated. EMG shows abnormal muscle activity suggestive of a myopathy. Muscle biopsy demonstrates perivascular lymphocytic infiltration of muscle

Tx: Prednisone is tried in severe cases with mixed responses. Poor response may be related to steroid myopathy which causes similar weakness pattern.

49
Q

Dermatomyositis

A

Presumed autoimmune attack against muscle with skin manifestations as well. May be paraneoplastic in some cases

Similar weakness pattern as polymyositis with associated skin changes consisting of a heliotrope rash on the eyelids, bridge of the nose, cheeks, elbows, knees and knuckles. Periorbital edema is frequent.

Dx: CPK is generally elevated. EMG shows abnormal muscle activity suggestive of a myopathy. Muscle bx shows perifascicular atrophy and inflammation

Tx: Prednisone like polymyositis. If the patient is greater than 40, a malignancy screen should be performed.

50
Q

Inclusion body myositis

A

Presumed autoimmune attack against muscle

Insidious, progressive muscle weakness involving FINGER FLEXORS AND LEG EXTENSORS. More common in middle aged males. Commonly misdiagnosed as polymyositis

Dx: CPK is elevated. EMG shows abnormal muscle activity suggestive of myopathy. Muscle bx shows interstitial infiltration but also “rimmed vacuoles”

Tx: Usually responds to prednisone. IVIG sometimes helpful. Generally progresses to a wheelchair bound state within 10 years

51
Q

Adult onset MDs

A

A groups of diseases caused by mutations in the genes coding for structural elements of muscle.

Four important forms:

1) Limb-girdle dystrophy - causes prox weakness presenting up to the 40s
2) Facio-scapulohumeral dystrophy - weakness in the face and shoulder girdle causing winged scapula
3) Oculopharyngeal dystrophy - causes progressive paresis of extraocular movements
4) Myotonic dystrophy - presents with both proximal AND distal weakness with associated cataracts, frontal balding and cardiac disturbance

Dx: CPK elevated mildly in these diseases with myopathic EMG. In myotonic dystrophy, myotonia can be demonstrated on EMG. Muscle bx shows fibers with various sizes as well as regenerating fibers. Specific mutations can be tested.

Tx: supportive care

52
Q

Endocrine myopathies

A

Cause not well defined. Well described in thyroid, parathyroid and adrenal disorders

Prox muscle weakness. Hypothyroidism also presents with muscle pain.

CPK may be elevated in some cases

Treatment of underlying endocrine deficiency or excess

53
Q

Toxic myopathies

A

Many drugs can cause muscle weakness by different mechanisms. Most common are the glucocorticoids, statins, zidovudine and gemfibrozil

Steroids generally produce painless prox muscle weakness

Statins can cause painful weakness with rhabdo and myoglobinuria

CPK very elevated in rhabdo. Acidosis may be seen as well as azotemia. In steroid myopathy, CPK usually normal

Tx: For rhabdo - aggressive hydration needed to prevent renal failure. For steroid - change to alternate day or switch to a steroid-sparing agent

54
Q

How do patients die from rhabdo?

A

Cardiac arrhythmia secondary to hyperK or ARF (acute protein load in kidneys)

Always order CK, lytes, renal studies

55
Q

3 major complications of rhabdo?

A

Cardiac arrest, ARF, compartment syndrome

56
Q

Causes of rhabdo?

A

NMS

Trauma (crush injury)

Reperfusion

Statins

Electrocution

57
Q

Various causes of neuropathy

A

1) Diabetes***
2) B12
3) B6 (low and high B6)
4) Pb, Hg, Thalium, Arsenic (get heavy metal panel)
5) Chemo
6) Isoniazid
7) Anti-metabolites (MTX, allopurinol, colchicine)
8) Amiodorone (anti-arrhythmics)
9) Alcohol
10) Syphilis
11) Lyme
12) HIV
13) Hep (esp C)
14) Autoimmune - vasculitis (patchy), Lupus, Sjogren, cryoglobulinemia
15) Thyroid (esp Hypo)
16) Plasma cell dyscrasias - MM, MGUS, Waldenstrom (get electropheresis)

58
Q

Dystrophin protein

A

Rod-shaped protein and a vital part of a protein complex that connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix through the cell membrane. Its gene is one of the longest known genes and accounts for 0.1% of genome

59
Q

Inheritance pattern of of duchenne and becker MD

A

X-linked mother to son

60
Q

Duchenne MD

A

Most common MD. Caused by absence of dystrophin (more mild version is Becker)

It’s a progressive proximal muscle weakness with characteristic enlargement (pseduohypertophy) of calves. Bulbar muscles (extraocular) are spared. Myocardium is affected.

Massive elevation of CK in blood, myopathic changes on EMG, myofiber degeneration with fibrosis and fatty infiltration on bx. It affects only males.

Without a FHx, unlikely to diagnose younger than 2 or 3. Most boys with DMD walk alone at a later age than average. Dx confirmed by muscle bx** and/or genetic testing.

the kid may have trouble rising from seated position or from a fall. Kid often pushes on his knees to upright himself. Toe walking.

Mutant dystrophin in neurons may cause lower IQ

Corticosteroids may help

61
Q

What distinguishes dermato from poly?

A

Dermatomyositis has a rash proceeding the muscle weakness. Also calcium deposits under skin.

Dermato has juvenile form (age 5-15), but is usually age 40-60. Can have dysphagia. Gottron papules on dorsum of metacarpophalangeal joint, prox interphalangeal, distal interphalangeal (lupus is on dorsum of fingers between the joints)

Poly in more gradual. Generally starts in 2nd decade. Rarely affects people under 18. Dysphagia more common.

IBM more gradual onset. Can be several years instead of 3-6months like the others. Men more than women. More resistant to treatment. Usually in older patients. Older than 50.

Neurology (14 decks)

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