What could be causing progressive weakness and numbness in a patient's left hand, particularly in digits 4 and 5, with recent onset of similar symptoms in the right hand after acupuncture, and a history of tingling in the left scapula and arm numbness when in a supine position?

Progressive Unilateral Hand Weakness with Bilateral Symptoms: Cervical Myelopathy Until Proven Otherwise

This presentation of progressive weakness starting in digits 4-5, now involving the thumb, with scapular tingling and positional arm numbness—especially with new contralateral symptoms after acupuncture—demands urgent MRI of the entire cervical spine without and with contrast to exclude cervical myelopathy, which is the most likely diagnosis. 1

Why This is Likely Cervical Myelopathy

Bilateral hand numbness with any lower extremity symptoms (or in this case, bilateral upper extremity involvement) demands urgent MRI of the entire cervical spine to exclude cervical cord pathology, particularly cervical spondylotic myelopathy. 1 The key features pointing to myelopathy include:

• Progressive motor weakness in a non-dermatomal pattern (digits 4-5 progressing to thumb involvement) suggests evolving myelopathy requiring immediate imaging and specialist evaluation 2
• Scapular tingling indicates involvement at the cervicothoracic junction, consistent with cord compression 1
• Positional symptoms (arm falling asleep when supine holding phone) suggest dynamic cord compression that worsens with neck positioning 1
• Bilateral progression after acupuncture may represent either coincidental disease progression or trauma-induced worsening of pre-existing cord compression 1
• Negative EMG months ago makes peripheral ulnar neuropathy less likely, though EMG can miss early or mild nerve pathology 3

Critical Red Flags Present

• Progressive motor weakness with sensory loss indicates evolving stroke, myelopathy, or Guillain-Barré syndrome requiring immediate imaging and specialist evaluation 2
• Bilateral hand involvement with upper extremity symptoms suggests cervical myelopathy requiring urgent neurosurgical consultation 3
• Central cord syndrome classically presents with greater upper extremity weakness than lower extremity involvement, with bilateral hand numbness and burning dysesthesias in forearms 1

Immediate Diagnostic Algorithm

First priority: Obtain MRI cervical spine without and with contrast within 24-48 hours. 1 Look for:

• Cord compression at any level (most commonly C5-C6 or C6-C7) 1
• Cord signal changes (T2 hyperintensity indicating myelomalacia) 1
• Stenosis with dynamic compression 1

Second priority: Perform focused neurological examination looking for:

• Dermatomal sensory testing with pinprick sensation, light touch, and two-point discrimination in C5-T1 distributions to diagnose cervical radiculopathy 3
• Wide-based gait with sensory ataxia, which suggests proprioceptive loss from cord involvement 1
• Hyperreflexia in lower extremities with upgoing toes (Babinski sign) indicating upper motor neuron involvement 1
• Hoffman's sign (flicking the middle finger nail causes thumb flexion) suggesting myelopathy 1

Alternative Diagnoses to Consider (Less Likely)

Peripheral Nerve Entrapment

• Carpal tunnel syndrome typically affects thumb, index, and middle fingers bilaterally, not digits 4-5 3
• Ulnar neuropathy would affect digits 4-5 but wouldn't explain thumb involvement, scapular symptoms, or bilateral progression 3
• Tinel's sign at wrist and Phalen's maneuver should be performed to rule out carpal tunnel syndrome 3

Cervical Radiculopathy

• Cervical radiculopathy presents with neck pain radiating to the arm in a dermatomal pattern with motor weakness or reflex changes 2
• This is less likely given the non-dermatomal distribution and bilateral progression 3

Vascular Causes (Unlikely but Must Exclude)

• Acute limb ischemia presents with the "6 P's": pulselessness, pallor, paresthesias, paralysis, coolness, and pain 2
• Check pulses immediately—absent pulses with unilateral symptoms require emergency vascular surgery consultation within 6 hours 2
• The presence of normal pulses and lack of pain/pallor makes this unlikely 2

Common Pitfalls to Avoid

• Do not assume peripheral neuropathy without excluding cervical myelopathy—urgent spinal imaging is required for bilateral hand involvement 1
• Do not assume bilateral symmetric neuropathy patterns (like diabetic or chemotherapy-induced neuropathy) with unilateral presentations 3
• Do not order routine EMG for suspected myelopathy—MRI is the diagnostic test of choice 1
• Do not delay imaging while pursuing conservative management—progressive motor weakness indicates evolving pathology 2

If MRI Confirms Myelopathy

Immediate neurosurgical consultation is required for confirmed cord pathology 1. Treatment options include:

• Surgical decompression (laminectomy, laminoplasty, or anterior cervical discectomy and fusion) depending on location and severity 1
• Conservative management only if mild compression without cord signal changes and stable symptoms 1

If MRI is Normal

Consider electrodiagnostic studies (nerve conduction studies and EMG) only if the clinical presentation remains uncertain after imaging 1. Then evaluate for:

• Multiple peripheral nerve entrapments 3
• Brachial plexopathy 4
• Thoracic outlet syndrome 4