What is the diagnosis and management for an adult patient with no significant past medical history presenting with tingling in both lower legs, arms, and back?

Bilateral Limb Paresthesias: Urgent Evaluation for Peripheral Polyneuropathy vs. Central Pathology

This patient requires immediate neurological examination to assess for rapidly progressive bilateral ascending weakness (Guillain-Barré syndrome) versus length-dependent peripheral polyneuropathy, with urgent MRI spine if any upper motor neuron signs, gait instability, or bowel/bladder dysfunction are present.

Critical Initial Assessment

Red Flag Symptoms Requiring Urgent Imaging

• Assess for compressive cervical myelopathy by checking for difficulty controlling arms or legs, very wobbly gait or legs giving way, pain between shoulder blades, and back/neck pain when lying down that disappears when sitting up 1
• Evaluate for Guillain-Barré syndrome by determining if weakness is rapidly progressive, bilateral, and ascending from legs to arms, with decreased or absent reflexes and acute/subacute onset with maximum disability within 2 weeks 1
• Order full spinal column MRI within 12 hours if there is any clinical suspicion of spinal cord compression or cauda equina syndrome, as MRI is superior to all other imaging modalities for demonstrating cord compression 1

Pattern Recognition for Peripheral Neuropathy

• Length-dependent polyneuropathy typically presents with sensory alterations in a "stocking and glove" distribution, starting distally in the feet and progressing proximally, with later involvement of hands 2
• Symmetric bilateral involvement of both upper and lower extremities simultaneously suggests either generalized polyneuropathy or central pathology (myelopathy), not focal nerve compression 3
• Paresthesias (tingling, numbness) without weakness favor sensory polyneuropathy over motor neuron disease or myopathy 4

Immediate Physical Examination Priorities

Neurological Examination Components

• Test deep tendon reflexes at ankles, knees, biceps, and triceps—areflexia or hyporeflexia suggests peripheral neuropathy, while hyperreflexia with clonus suggests myelopathy 5
• Assess sensory modalities including pinprick, light touch, vibration (using 128 Hz tuning fork), and joint position sense in distal extremities 2, 4
• Evaluate motor strength proximally and distally in all four extremities—distal weakness with preserved proximal strength suggests peripheral neuropathy, while proximal and distal weakness suggests inflammatory neuropathy like CIDP 5
• Check for Romberg sign (increased sway with eyes closed) and assess gait for steppage pattern or foot drop, which indicate proprioceptive loss from large fiber neuropathy 5
• Test for sensory level on the trunk—presence of a sensory level strongly suggests myelopathy rather than peripheral neuropathy 1

Critical Distinction: Upper vs. Lower Motor Neuron

• Upper motor neuron signs (hyperreflexia, spasticity, Babinski sign, clonus) indicate central pathology requiring urgent MRI spine 1
• Lower motor neuron signs (hyporeflexia/areflexia, flaccid weakness, muscle atrophy) indicate peripheral nerve pathology 3

Initial Laboratory Workup

First-Line Blood Tests

• Order complete blood count, comprehensive metabolic profile, fasting blood glucose, vitamin B12, thyroid-stimulating hormone, and serum protein electrophoresis with immunofixation as initial evaluation for treatable causes of peripheral neuropathy 2
• Check hemoglobin A1c to assess for diabetes mellitus, the most common identifiable cause of peripheral neuropathy 2
• Measure vitamin B12 level as deficiency causes subacute combined degeneration affecting both peripheral nerves and spinal cord 2

When to Pursue Advanced Testing

• Refer to neurology for electrodiagnostic studies (EMG/NCS) if initial examination suggests peripheral neuropathy, as these studies differentiate between demyelinating and axonal patterns and help confirm diagnosis 1, 2
• EMG/NCS showing demyelinating pattern with conduction blocks and nonuniform slowing suggests inflammatory neuropathy (CIDP or GBS) requiring immunotherapy 5
• Consider lumbar puncture if GBS or CIDP suspected—acellular cerebrospinal fluid with elevated protein (albuminocytologic dissociation) supports these diagnoses 5

Treatment Based on Diagnosis

If Guillain-Barré Syndrome Confirmed

• Initiate immunotherapy immediately with either intravenous immunoglobulin (IVIG) or plasma exchange, as these are equally effective and should be started as soon as possible 1
• Monitor respiratory function closely as weakness of respiratory muscles is a life-threatening manifestation requiring urgent therapeutic decisions 3

If Chronic Peripheral Neuropathy

• Treat underlying etiology once identified (optimize glucose control for diabetic neuropathy, replace vitamin B12 for deficiency, discontinue offending medications or toxins) 2
• For neuropathic pain symptoms, offer duloxetine as first-line pharmacotherapy, supported by Level IB evidence for neuropathic symptoms 1
• Consider gabapentinoids (gabapentin or pregabalin) as alternative agents to alleviate neuropathic pain 2

Common Pitfalls to Avoid

• Do not delay imaging while pursuing conservative management if any alarm symptoms are present (gait instability, bowel/bladder dysfunction, upper motor neuron signs), as this can lead to irreversible neurological damage 1
• Do not assume bilateral symptoms are benign or musculoskeletal, as bilateral presentation can indicate serious central pathology like myelopathy or GBS 1
• Do not miss rapidly progressive weakness by attributing symptoms solely to sensory complaints—GBS can progress to respiratory failure within days 1, 3
• Do not overlook treatable causes by accepting "idiopathic neuropathy" diagnosis without completing initial laboratory evaluation, as 25-46% of cases remain idiopathic only after thorough workup 2