Wasted Hands

Relevant physical signs

• Inspection
  • Myotonic facies
  • Ipsilateral Horner’s syndrome (Pancoast’s tumour)
  • Tongue fasciculations (motor neurone disease)
  • Symmetry
  • Fasciculations
  • Distribution
    • Muscles innervated by median nerve (thenar eminence)
    • Muscles innervated by ulnar nerve (hypothenar eminence)
    • Generalized wasting (C8/T1 anterior horn cell disease / plexopathy)
  • Involvement of the lower limbs
    • Foot drop (myotonic dystrophy, inclusion body myositis)
    • Pes cavus (Charcot-Marie-Tooth disease)
  • Clawing of the hand (C8/T1 lesion or combined median / ulnar nerve palsy)
  • Deforming polyarthropathy (disuse atrophy from rheumatoid arthritis)
  • Clubbing (Pancoat’s tumour, especially if unilateral)
• Tone
  • Flaccid as wasting is a sign of lower motor neurone disease
  • Spastic lower limbs if cervical myelopathy
• Reflexes
  • Normal biceps, supinator, triceps if C8-T1 cord lesion
  • May be depressed if cord lesion is multi-level / peripheral neuropathy
• Power
  • “Point your thumb to the ceiling” – flexor pollicis brevis, median nerve
  • “Push your thumb inwards” – abductor pollicis brevis, median nerve
  • “Make a fist” – hand of Benediction in median nerve palsy
  • “Make an OK sign, then touch each finger with your thumb) – opponens pollicis, median nerve
  • “Hold this piece of paper between your fingers” – palmar interossei, ulnar nerve
  • “Hold this piece of paper between your thumb and index finger” – if the thumb flexes to compensate, this is a positive Froment’s sign and indicates ulnar nerve palsy
  • Check flexion of the DIPJ of the 5^th finger in ulnar nerve palsy – if preserved, lesion is distal to elbow
  • Wrist extension – radial nerve, C7/8
• Coordination usually normal
• Sensation
  • Check for sensory loss in distribution of median, ulnar and radial nerves
  • If glove and stocking loss: peripheral neuropathy such as Charcot-Marie-Tooth
  • If dissociated sensory loss to pain and temperature only: syringomyelia
  • If proprioception affected more: cervical myelopathy
  • If sensation completely preserved
    • Anterior horn cell disease e.g. old poliomyelitis
    • Motor neurone disease
    • Myotonic dystrophy
    • Inclusion body myositis
    • Distal spinal muscular atrophy

Differential diagnosis

• Cervical myelopathy
• Anterior horn cell disease
• Motor neurone disease
• C8/T1 radiculopathy
  • Pancoast’s syndrome
• Lower brachial plexopathy
  • Cervical rib
• Mononeuropathy
• Charcot-Marie-Tooth disease
• Myotonic dystrophy
• Inclusion body myositis
• Distal spinal muscular atrophy
• Disuse atrophy

Investigations

• Nerve conduction studies: to look for slowing of conduction across affected nerves
• Chest radiograph
  • Cervical rib
  • Pancoast tumour
• Magnetic resonance imaging of the cervical spine to look for cervical myelopathy
• EMG to look for electrical myotonia if myotonic dystrophy suspected
• Muscle biopsy if inclusion body myositis

Management

• Patient education
• PT/OT to maximize and preserve function
• Compression neuropathies may require decompressive surgery (e.g. carpal tunnel release)
• Treat the underlying cause

Summary

Sir, this patient has asymmetric wasting of the small muscles of the right hand. On examination, there is weakness of muscles supplied by the median nerve, such as abductor pollicis brevis and flexor pollicis brevis, as well as those supplied by the ulnar nerve, such as the palmar interossei. Wrist extension and finger flexion are relatively spared, implying that this is a C8/T1 lesion. Sensation is also lost to pinprick in those dermatomes. The possibilities for this include a C8/T1 radiculopathy or a lower brachial plexopathy. This may be caused by low cervical spondylosis, although it usually affects the middle cervical cord, an apical lung tumour, although I did not see any overt ipsilateral Horner’s syndrome, a cervical rib, or traumatic avulsion of the brachial plexus.

In summary, this patient has a C8/T1 lesion, causing unilateral wasting of the small muscles of the hand.