What causes numbness in the right buttock, leg, trunk, and arm?

Numbness in Right Buttock, Leg, Trunk, and Arm: Differential Diagnosis and Evaluation

Immediate Assessment Priority

This distribution of numbness affecting multiple body regions on one side (right buttock, leg, trunk, and arm) suggests either central nervous system pathology (cervical spinal cord compression or stroke) or multiple peripheral nerve involvement, requiring urgent neurological evaluation. 1, 2

Key Diagnostic Considerations

Central Spinal Cord Pathology (Most Likely)

• Cervical myelopathy can present with lower extremity symptoms without upper extremity involvement, making it a critical consideration even when arm symptoms seem less prominent 2
• Cervical spinal cord compression at C6-C7 or higher levels can cause bilateral or unilateral leg weakness, numbness, and autonomic dysfunction (bowel/bladder changes) 2
• The combination of trunk, arm, and leg numbness on the same side strongly suggests a cervical cord lesion affecting multiple spinal levels 1, 3

Peripheral Vascular Disease

• Iliac artery occlusive disease can produce buttock, hip, and thigh numbness along with leg symptoms 1
• However, vascular claudication typically does not cause trunk or arm numbness, making this less likely as the sole explanation 1

Stroke/Central Nervous System Event

• Sudden numbness of the face, arm, or leg on one side of the body is a cardinal sign of stroke 1
• The involvement of trunk, arm, and leg suggests possible cortical or subcortical lesion 1

Recommended Diagnostic Algorithm

Step 1: Determine Onset Pattern

• Sudden onset (minutes to hours): Activate emergency stroke protocol immediately - this is a medical emergency requiring immediate imaging and potential intervention 1
• Subacute/progressive onset (days to weeks): Proceed with urgent spinal cord evaluation 1, 2

Step 2: Assess for Red Flag Symptoms

• Bowel or bladder dysfunction (difficulty initiating urination, constipation, incontinence): Suggests cauda equina syndrome or cervical myelopathy requiring urgent MRI 1, 2
• Progressive bilateral leg weakness: Indicates possible cervical myelopathy even without prominent upper extremity symptoms 2
• Gait disturbance or balance problems: Suggests central nervous system involvement 1, 2
• Saddle numbness or perianal sensory changes: Indicates cauda equina syndrome requiring emergency evaluation 1

Step 3: Initial Imaging Based on Clinical Presentation

For suspected cervical myelopathy (progressive symptoms, multiple dermatome involvement):

• MRI cervical spine without contrast is the definitive initial study 1, 4
• Must image cervical spine even when lower extremity symptoms predominate, as cervical stenosis can present with isolated leg symptoms 2
• Look specifically for spinal cord signal changes from C3-C7, canal stenosis, and nerve root compression 1, 4

For suspected stroke (sudden onset):

• Immediate CT head without contrast to rule out hemorrhage, followed by MRI brain if ischemic stroke suspected 1

For suspected lumbar pathology (if cervical imaging negative):

• MRI lumbar spine without contrast to evaluate for nerve root compression at L5-S1 or cauda equina syndrome 1, 4

Step 4: Assess Vascular Contribution

• If symptoms are exercise-induced and relieved by rest, consider ankle-brachial index (ABI) testing 1
• Iliac artery disease produces buttock and thigh claudication but would not explain trunk or arm symptoms 1

Critical Clinical Pitfalls

• Do not assume lumbar pathology explains all lower extremity symptoms - cervical myelopathy commonly presents with leg symptoms without hand clumsiness 2
• Do not delay imaging for "conservative management" when multiple dermatomes are involved or progressive neurological deficits are present 1, 2
• Spinal immobilization devices should not be used by first aid providers unless specifically trained, as they may cause harm 1
• Postoperative patients with new numbness require immediate evaluation for complications such as epidural hematoma or worsening compression 1, 4

Specific Anatomic Correlations

• Buttock numbness: L5-S1 nerve roots, iliac artery disease, or sacral plexus involvement 1, 4
• Leg numbness: Can arise from lumbar (L3-S1), cervical cord (if bilateral/progressive), or vascular causes 1, 2
• Trunk numbness: Suggests thoracic or cervical spinal cord involvement at the corresponding dermatome level 3, 2
• Arm numbness: Cervical nerve roots (C5-T1), brachial plexus, or central lesion 1, 3

Urgent Referral Indications

• Age ≥65 years with new neurological symptoms 1
• Progressive weakness or sensory deficit involving multiple extremities 1
• Any bowel or bladder dysfunction 1, 2
• Symptoms following trauma (even minor falls in older adults) 1
• Sudden onset suggesting stroke 1

If symptoms are progressive or involve multiple body regions, cervical spine MRI should be obtained urgently (within 24-48 hours) even if upper extremity examination appears normal, as cervical myelopathy can present with predominantly lower extremity findings. 2, 4