Weakness

Background

Acute/Generalized

Workup

1. cbc
2. chem 10 (esp. K, Mg, Ca, Phos)
3. ecg
4. +/- CK (r/o myopathy)
5. +/- FVC (eval impending resp failure, i.e. Myasthenia)
6. +/- ABG/CT/LP/TSH/UA (rhabdo)

Diagnosis

UPPER MOTOR NEURON

1. BRAIN

• Weakness - variable
• Bowel/Bladder -
• Reflexes - increased
• Sens - diminished
• Pain - no
• Asymmetric/unilateral

1. CORD

• Weakness - fixed level

    Bowel/Bladder - YES

    Reflexes - increased

    Sens - diminished

    Pain - +/-

LOWER MOTOR NEURON

III. NERVE

    Weakness - distal and ascends

    Bowel/Bladder - NO

    Reflexes - diminished

    Sens - nl/paresthesias

    Pain - no

END-PLATE/MUSCLE

IV. MOTOR END PLATE

    Weakness - head and descends

    Bowel/Bladder - NO

    Reflexes - nl/diminished

    Sens - nl

    Pain - no

V. MUSCLE

    Weakness - proximal

    Bowel/Bladder - NO

    Reflexes - nl/diminished

    Sens - nl

    Pain - +/-

DIFFERENTIAL DIAGNOSIS

I. UPPER

    A) Multiple sclerosis

    B) Poliomyelitis

    C) ALS (upper & lower motor)

II. CORD

    A) Painful

         i) Cord compression

    B) Painless

         i) Transverse myelitis

         ii) Spinal cord infarct

         iii) Intramedullary tumor

III. NERVE

    A) Guillian-Barre

    B) Toxic neuropthy (Ciguatera)

    C) Tick paralysis

    D) Diabetic neuropathy

    E) Porphyria

IV. MOTOR END PLATE

    A) Myasthenia gravis

    B) Botulism (descending)

    C) Organophosphate poisoning

    D) Lambert-Eaton

V. MUSCLE

    A) Painful

         i) Rhabdo

         ii) Alcoholic

         iii) Myopathy

         iv) Polymyositis

         v) Dermatomyositis

         vi) Toxins

         vii) Hypophos

         viii) Hypo-kalemia

         ix) Polymyalgia rheum

    B) Painless

         i) Familial periodic paralysis

         ii) Endocrine

VI. MIXED

    A) Upper & Lower Motor Neuron

         i) ALS

    B) Sensory & Motor

         i)

VII. NON-NEUROMUSCULAR

    A) MI

    B) Resp failure

    C) Sepsis

    D) Dehydration

    E) Anxiety

    F) Fibromyalgia/chronic fatigue

    G) Malignancy

EMERGENT THREAT/ED WORKUP

I. CORD

    - paralysis

    - MRI, neurologist

2. NERVE

    - resp failure

    - FEV1, airway mgt, ticks?, neurologist

3. MOTOR END PLATE

    - resp failure

    - FEV1, airway mgt, Tensilon Test?

4. MUSCLE

    - Rhabdo

    - urine myoglobin, serum CK, BUN/Cr

    serum K+

INTUBATION INDICATIONS

1) Severe fatigue

2) Inability protect airway

3) Rapidly increasing PaCO2

4) Hypoxemia despite O2

5) FVC <12 mL/kg

6) Neg Insp Force <20 cm H2O

2/26/06 DONALDSON (adapted from Rosen, Lampe, Birnbaumer)

adapted from Hockberger