What is the cause of sudden onset paresthesia in a 48-year-old male with well-controlled type 2 diabetes, hypertension, and hyperlipidemia, taking simvastatin, Farxiga (dapagliflozin), metformin, daily Aspirin (acetylsalicylic acid) 81mg, fish oil, and vitamin D, presenting with pins and needles sensation in his left forearm and hand/fingers without any history of trauma or injury?

Evaluation of Sudden Onset Left Upper Extremity Paresthesias

This patient requires urgent evaluation for cervical radiculopathy or nerve entrapment, most likely C6-C7 radiculopathy or ulnar/median nerve compression, given the sudden onset unilateral upper extremity paresthesias following chiropractic manipulation. 1

Immediate Diagnostic Priorities

Most Likely Diagnosis: Cervical Radiculopathy or Nerve Entrapment

The clinical presentation strongly suggests a mechanical nerve injury rather than diabetic neuropathy because:

• Diabetic neuropathy presents with distal symmetric stocking-glove distribution affecting feet and legs first, not sudden unilateral upper extremity symptoms 2, 3
• Sudden onset unilateral paresthesias in the forearm and hand following chiropractic manipulation points to mechanical nerve injury 1
• The patient's diabetes is well-controlled, making acute diabetic neuropathy progression unlikely 2

Critical Red Flags to Assess Immediately

Evaluate for these emergent conditions that require immediate intervention:

• Motor weakness in the affected limb - suggests nerve root compression or mononeuropathy requiring urgent imaging 1
• Bilateral symptoms or progression to other limbs - could indicate central pathology (brainstem or spinal cord lesion) 3
• Bowel/bladder dysfunction - indicates cauda equina syndrome requiring emergency surgical decompression 1
• Severe dysautonomia - suggests Guillain-Barré syndrome requiring hospitalization 1

Differential Diagnosis in Order of Likelihood

1. Cervical Radiculopathy (C6-C7)

• The scapular manipulation by the chiropractor could have caused nerve root irritation or disc herniation 1
• C6-C7 radiculopathy classically causes paresthesias in the forearm and hand/fingers 1
• Obtain cervical spine MRI with and without contrast to evaluate for disc herniation, foraminal stenosis, or nerve root compression 2

2. Ulnar or Median Nerve Entrapment

• Carpal tunnel syndrome (median nerve) is the most common cause of hand paresthesias 1
• Ulnar nerve entrapment at the elbow can cause forearm and hand symptoms 1
• The patient's occupation as an MRI tech with repetitive lifting/positioning increases risk 1
• Perform nerve conduction studies and ultrasonography to confirm nerve entrapment and identify the specific site 3, 1

3. Thoracic Outlet Syndrome

• Can cause upper extremity paresthesias, particularly with overhead activities 1
• Less likely given the sudden onset and lack of positional variation 1

4. Diabetic Mononeuropathy (Less Likely)

• Diabetic neuropathy typically presents symmetrically and distally, not with sudden unilateral upper extremity symptoms 2, 3
• His well-controlled diabetes (HbA1c presumably <7%) makes acute diabetic neuropathy unlikely 2
• However, diabetes does increase susceptibility to nerve compression injuries 2

Essential Diagnostic Workup

Immediate Physical Examination Elements

Perform detailed neurological examination focusing on:

• Cervical spine range of motion and Spurling's test (neck extension with lateral rotation reproduces radicular symptoms) 1
• Motor strength testing of C5-T1 myotomes - weakness indicates nerve root or peripheral nerve injury 1
• Sensory testing in dermatomal distribution to localize the affected nerve root 1
• Deep tendon reflexes (biceps C5-C6, triceps C7, brachioradialis C6) - asymmetry suggests radiculopathy 1
• Tinel's sign at wrist and elbow for carpal tunnel and cubital tunnel syndrome 1
• Phalen's test for carpal tunnel syndrome 1

Imaging and Electrodiagnostic Studies

Order cervical spine MRI with and without contrast as first-line imaging to evaluate for:

• Disc herniation 2
• Foraminal stenosis 2
• Spinal cord compression 2
• Mass lesions or inflammatory processes 2

Obtain nerve conduction studies and EMG if:

• MRI is negative for radiculopathy 3, 1
• Clinical suspicion for peripheral nerve entrapment is high 3, 1
• Symptoms persist beyond 4-6 weeks 1

Ultrasonography of peripheral nerves can identify:

• Nerve enlargement and hypoechogenicity at entrapment sites 1
• Space-occupying lesions compressing nerves 1
• Anatomical variations predisposing to entrapment 1

Laboratory Testing (Lower Priority)

While less likely given the clinical presentation, check the following to exclude systemic causes:

• Vitamin B12 level - deficiency can cause paresthesias but typically symmetric 3, 4
• TSH - hypothyroidism can cause carpal tunnel syndrome 1
• Lyme serology if in endemic area - can cause both facial and peripheral neuropathy 3
• HbA1c - confirm diabetes control (though already reported as well-controlled) 2

Management Approach

Conservative Management (First-Line)

Initiate conservative treatment while awaiting diagnostic workup:

• Avoid provocative activities including repetitive lifting and neck movements 1
• NSAIDs for anti-inflammatory effect if no contraindications 1
• Physical therapy with cervical traction and nerve gliding exercises if radiculopathy is suspected 1
• Wrist splinting at night if carpal tunnel syndrome is suspected 1

When to Escalate Care

Refer urgently to neurosurgery or orthopedic spine surgery if:

• Progressive motor weakness develops 1
• MRI shows significant nerve root or spinal cord compression 2
• Symptoms worsen despite 6-8 weeks of conservative management 1

Refer to neurology if:

• Electrodiagnostic studies show demyelinating pattern suggesting inflammatory neuropathy 3
• Multiple nerve distributions are affected 3
• Symptoms suggest central rather than peripheral pathology 3

Ultrasound-Guided Interventions

Consider ultrasound-guided corticosteroid injection for:

• Confirmed carpal tunnel syndrome with moderate symptoms 1
• Cubital tunnel syndrome 1
• Cervical epidural steroid injection for radiculopathy (performed by pain management or spine specialist) 1

Critical Pitfalls to Avoid

Do not attribute symptoms to diabetic neuropathy without excluding mechanical causes - the sudden onset, unilateral distribution, and temporal relationship to chiropractic manipulation strongly suggest mechanical injury rather than metabolic neuropathy 2, 1

Do not delay imaging if any motor weakness is present - progressive weakness indicates nerve compression requiring urgent intervention 1

Do not miss central pathology - if facial paresthesias or bilateral symptoms develop, this suggests brainstem or central pathology requiring immediate neuroimaging 3

Do not overlook vascular causes in diabetic patients - while less likely here, diabetic patients with vascular access or peripheral arterial disease can develop steal syndrome causing hand ischemia and paresthesias 2

Prognosis and Follow-Up

Most cases of cervical radiculopathy and nerve entrapment improve with conservative management over 6-12 weeks 1

Schedule follow-up in 2-4 weeks to reassess symptoms and review diagnostic results 1

If symptoms persist beyond 3 months despite conservative treatment, surgical decompression should be considered 1