1. Motor disorders
Motor neuron disease
Myasthenia gravis
Muscular dystrophy

2. Motor neuron disease
 Affects motor neurons-
upper-cortical &/or lower-spinal-anterior horn
 Cause- 90% sporadic,
~10% familial- commonest SOD1 mutation
 s/s-
 LMN- progressive weakness, wasting, fasciculation
 UMN- spasticity, exaggerated DTRs, extensor plantar
 Classification-
 ALS- amytropic lateral sclerosis- UMN + LMN
 PLS- primary lateral sclerosis- UMN
 PMA- progressive muscular atrophy-LMN
 Bulbar-LMN & pseudobulbar-UMN palsy

3. Management
 Dx-
 Clinical
 NCV/EMG
 MRI of cervical spine
 Blood tests- TSH, K, Ca, PO4, CPK, VDRL, ANA
 Rx-
 Supportive
 Riluzole- a glutamate inhibitor, for bulbar palsy
 Px-
 Death commonly due to respiratory complications
 ~20% 5 year & ~10% 10 year survival

4. Myasthenia gravis
 An autoimmune disorder, leading to
fluctuating muscle weakness & fatiguability
 Auto-antibodies block acetylcholine receptor
at post-synaptic neuromuscular junction
 s/s- intermittent
 Ptosis, diplopia
 Unstable gait, limb weakness
 Dysphagia, dysarthria, facial muscle weakness
 ~75% have thymus abnormality,
~25% have thymoma

5. Classification
 Class I- ptosis only
 II- + mild weakness of other muscles
IIa- limb/axial
IIb- bulbar/respiratory
 III- + moderate weakness- a/b
 IV- + severe weakness- a/b
 V- requiring mechanical ventilation

6. Diagnosis
 Symptoms +
 Signs of fatiguability of muscles
 Acetylcholine receptor Ab
 EMG- repetitive nerve stimulation test
 IV Edrophonium/Neostigmine test-
temporarily relieve weakness
 CxR/CT scan/MRI- for thymoma
 PFT- spirometry- to assess lung function

7. Treatment
 Drugs-
 Cholinesterase inhibitors- improve muscle function-
Pyridostigmine
 Immunosuppressants- prednisone, cyclosporine,
mycophenolate mofetil, azathioprine
 IVIG/plasmapheresis- in emergency
 Surgery-
Thymectomy, beneficial specially for thymoma

8. Muscular dystrophy
 A group of inherited disorders
 Onset- usually in childhood
 Cause progressive muscle weakness &
wasting leading to falls, difficulty walking,
waddling gait
 Dx- based on specific muscle involvement,
muscle biopsy & raised CPK
 Rx- supportive

9. Types
 Duchenne-
 Commonest
 X-linked recessive; males affected, females carrier
 Due to absence of dystrophin protein
 Onset in childhood
 Causes pseudohypertrophy of calves
 Becker- less severe variant of Duchenne
 Myotonic-
 Commonest in adults, onset- 20-40 years
 Autosomal dominant inheritance
 Affects skeletal, smooth & cardiac muscle
 Facioscapulohumeral
 Limb girdle

10. Types
 Duchenne-
 Commonest
 X-linked recessive; males affected, females carrier
 Due to absence of dystrophin protein
 Onset in childhood
 Causes pseudohypertrophy of calves
 Becker- less severe variant of Duchenne
 Myotonic-
 Commonest in adults, onset- 20-40 years
 Autosomal dominant inheritance
 Affects skeletal, smooth & cardiac muscle
 Facioscapulohumeral
 Limb girdle