SPOTTERS
MEDICINE
WASTING OF SMALL MUSCLES OF HANDS
🔹 Definition:
Wasting of
the small muscles of the hand refers to atrophy of intrinsic hand muscles
(thenar, hypothenar, interossei, and lumbricals), leading to loss of muscle
bulk and hand function.
🔹 Common Muscles Involved:
- Thenar muscles – affected in median nerve
lesions
- Hypothenar muscles – affected in ulnar nerve
lesions
- Interossei and lumbricals – affected in lower motor
neuron (LMN) lesions
🔹 Clinical Features:
- Visible hollowing in
intermetacarpal spaces
- Weak grip strength
- Claw hand or ape thumb deformities
- Difficulty in fine motor tasks
(buttoning, writing)
- May be painless or with
associated sensory loss
🔹 Causes:
🔸 Neurological:
1.
Lower Motor Neuron Lesions:
o Ulnar nerve palsy (e.g., cubital tunnel syndrome)
o Median nerve palsy (e.g., carpal tunnel syndrome)
o Combined nerve injuries (e.g., brachial plexus injury)
2.
Anterior Horn Cell Diseases:
o Amyotrophic Lateral Sclerosis (ALS)
o Spinal Muscular Atrophy
o Syringomyelia (cervical cord cavity expansion)
3.
Peripheral Neuropathies:
o Diabetic neuropathy
o Leprosy
o Alcoholic neuropathy
4.
Cervical Spondylotic Myelopathy:
o Compression of spinal cord at C8–T1
🔸 Muscular Causes:
- Myopathies (less common cause of
focal wasting)
🔸 Others:
- Disuse atrophy
- Post-traumatic nerve injury
- Chronic joint diseases (e.g.,
rheumatoid arthritis)
🔹 Investigations:
- Neurological examination – tone, power, reflexes,
sensations
- Nerve conduction studies &
EMG
- MRI Cervical spine – to detect cord compression or
syrinx
- Blood tests – for diabetes, infections,
autoimmune markers
- Nerve biopsy (in specific cases, e.g.,
leprosy)
🔹 Treatment:
- Depends on underlying cause
- Surgical decompression (e.g.,
carpal tunnel, cervical spondylosis)
- Physiotherapy and splinting
- Disease-modifying treatment
(e.g., immunotherapy for ALS, MDT for leprosy)
- Vitamin supplementation (e.g.,
B12)
- Diabetes control in neuropathy
🔹 Prognosis:
- Reversible if caught early in compressive
or metabolic causes
- Progressive in neurodegenerative diseases
like ALS
- Requires multidisciplinary
rehabilitation for function preservation
DR.C.GANESAN
M.D.,
PROFESSOR OF
MEDICINE
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