Progressive Distal Weakness
This condition mostly occurs due to myopathies, followed by neuropathies.
1. Myopathies
The myopathies are primary disease of muscle, and all produce weakness
with variable pain and wasting of skeletal muscles.
a) Muscular dystrophies
i. Duchene muscular dystrophy
ii. Becker muscular dystrophy
iii. Facioscapulohumeral dystrophy
iv. Limb girdle dystrophy
v. Myotonic dystrophy
b) Metabolic myopathies
i. Glycogenoses: Myophosphorylase deficiency, acid maltase deficiency,
phosphofructokinase deficiency
ii. Lipidoses: Carnitine deficiency, carnitine palmityl transferase
deficiency
iii. Endocrine myopathies: Hyperthyroidism, hypothyroidism, hyperparathyroidism,
corticosteroid myopathy
iv. Periodic paralysis: Hyperkalemic, hypokalemic
v. Mitochondrial myopathies
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− Kearns-Sayre syndrome (external ophthalmoplegia, retinitis
pigmentosa, heart block elevated CSF protein)
− Myoclonic epilepsy with ragged red fibres (MERRF)
− Mitochondrial encephalopathy with lactic acidosis and strokelike
episodes (MELAS)
− Pure skeletal myopathy
c) Inflammatory myopathies
Acquired muscle diseases in which muscle inflammation produces variable
amounts of weakness and pain.
i. Dermatomyositis
ii. Polymyositis
iii. Inclusion body myositis
2. Peripheral neuropathies
This type of neuropathy produces signs and symptoms in a distal-to-proximal
gradient, the so-called stocking-glove pattern.
a) Idiopathic chronic neuropathy
i. Axonal form
ii. Demyelinating form
b) Hereditary motor and sensory neuropathy
i. Type I: Charcot–Marie–Tooth disease
ii. Type II: Charcot–Marie–Tooth disease, neuronal type
iii. Type III: Dejerine–Sottas disease
iv. Type IV: Refsum disease
c) Other genetic neuropathies
i. Giant axonal neuropathy
ii. Metachromatic leukodystrophy
d) Toxic/metabolic neuropathies
i. Toxins: Mercury, lead, zinc, arsenic, thallium, alcohol, organophosphates
ii. Drugs: Amiodarone, Cis-platinum, dapsone, INH, phenytoin, pyridoxine,
vincristine, Nitrofurantoin, ddi, ddc
e) Neuropathies associated with systemic disease
i. Systemic diseases: Diabetes mellitus, uremia, porphyria, vitamin
B12 deficiency, amyloidosis, hypothyroidism, benign monoclonal
gammopathy
ii. Systemic infections: Leprosy, syphilis, diphtheria, HIV
iii. Vasculitis due to ischemic infarction of vasa vasorum: Systemic
lupus erythematosus, rheumatoid arthritis, polyarteritis nodosa,
cryoglobulinemia
iv. Cancer: Hodgkin’s disease, multiple myeloma, oat cell carcinoma
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f) Immune-mediated neuropathies
i. Guillain–Barre syndrome
ii. Chronic inflammatory demyelinating polyneuropathy
3. Motor neuron disease (anterior horn cell diseases)
a) Lower motor neuron signs present
i. Spinal muscular atrophy
ii. Infantile (Werding–Hoffman disease)
iii. Juvenile (Kugelberg–Welander disease)
iv. Adult (Aran–Duchene)
b) Lower and upper motor signs present
i. Amyotrophic lateral sclerosis (motor neuron disease)
ii. Progressive bulbar palsy
c) Upper motor signs present
i. Lateral sclerosis
4. Spinal cord disorders
a) Congenital malformations
i. Arteriovenous malformations
ii. Myelomeningocele
iii. Chiari malformation (type I and II)
iv. Tethered spinal cord
v. Atlantoaxial dislocation: Aplasia of odontoid process, Morquio
syndrome, Klippel–Feil syndrome
b) Familial spastic paraplegia
c) Trauma
i. Spinal cord concussion
ii. Compressed vertebral body fractures
iii. Fracture dislocation and spinal cord transection
iv. Spinal epidural hematoma
d) Tumors of the spinal cord
i. Astrocytoma
ii. Ependymoma
iii. Neuroblastoma
iv. Other tumors: sarcoma, neurofibroma, dermoid/epidermoid,
meningioma, teratoma
e) Transverse myelitis
f) Neonatal cord infarction
g) Infections
i. Diskitis
ii. Epidural abscess
iii. Tuberculous osteomyelitis