What are the potential causes of left buttock tingling and numbness in a patient?

Left Buttock Tingling and Numbness: Differential Diagnosis

The most common causes of unilateral left buttock tingling and numbness are lumbosacral radiculopathy, piriformis syndrome/deep gluteal syndrome with sciatic nerve compression, peripheral arterial disease affecting the iliac or gluteal arteries, and cluneal nerve entrapment.

Neurogenic Causes

Lumbosacral Radiculopathy and Spinal Stenosis

• Lumbar spine pathology is the primary consideration when buttock symptoms are accompanied by leg pain, paresthesias, or weakness. 1
• Neurogenic claudication from spinal stenosis typically presents with buttock and leg symptoms that worsen with walking and improve with rest or forward flexion of the trunk. 1
• Distinguish from vascular claudication: neurogenic symptoms often take longer than 10 minutes to resolve with rest and may be accompanied by paresthesias. 1

Piriformis Syndrome and Deep Gluteal Syndrome

• Piriformis syndrome causes buttock tenderness with sciatica-like pain radiating posteriorly, often triggered by sitting or hip flexion, adduction, and internal rotation. 2, 3
• The posterior femoral cutaneous nerve is frequently involved, causing posterior thigh pain that may be more prevalent than leg/foot pain. 2
• Posttraumatic cases occur after blunt buttock trauma, with patients experiencing intolerance to sitting, tenderness at the greater sciatic notch, and radicular symptoms. 3
• MRI or ultrasound can identify sciatic neuritis, peri-sciatic pathology including neural compression, and peri-neural adhesions or fibrosis in the subgluteal space. 4
• Anatomical variants of pelvic girdle muscles, muscle spasm, and pelvic instability contribute to nerve entrapment. 4

Cluneal Nerve Entrapment

• Entrapment of cluneal nerves at the iliac crest can cause "pseudo-sciatica" with buttock numbness and tingling. 4

Vascular Causes

Peripheral Arterial Disease

• Occlusive disease in the iliac arteries produces hip, buttock, and thigh pain, as well as calf pain, with symptoms occurring during exercise and relieving with rest. 1
• Proximal arterial stenosis (aortic bifurcation, common iliac, or hypogastric arteries) causes buttock pain that forces patients to stop walking, improves within 1-2 minutes, and recurs with resumed activity. 5
• Physical examination should document femoral, popliteal, posterior tibial, and dorsalis pedis pulses; femoral bruits may indicate focal stenoses. 1
• Hypogastric or gluteal artery stenosis may not reduce ankle-brachial index if there is no substantial aorto-iliac damage. 5
• Doppler ultrasound confirms arterial stenosis; CT angiography is indicated if mesenteric ischemia is suspected with atherosclerotic risk factors. 6, 5

Key Distinguishing Features

Clinical History Red Flags

• Assess whether symptoms occur at rest versus with activity, time to symptom relief, and presence of positional triggers. 1
• Vascular claudication: symptoms during walking, relief within 10 minutes of rest, no improvement during continued walking. 1
• Neurogenic claudication: symptoms during walking, relief may take >10 minutes, improvement with forward trunk flexion. 1
• Piriformis syndrome: intolerance to sitting, pain with specific hip movements, history of buttock trauma. 3

Physical Examination Findings

• Diminished pulses suggest vascular etiology; normal pulses do not exclude hypogastric/gluteal artery disease. 1, 5
• Tenderness at greater sciatic notch with pain on hip flexion, adduction, and internal rotation suggests piriformis syndrome. 3
• Palpable tenderness along iliac crest may indicate cluneal nerve entrapment. 4

Diagnostic Approach

Initial Workup

• Obtain ankle-brachial index (ABI) to screen for peripheral arterial disease; post-exercise ABI if resting ABI is normal but vascular claudication is suspected. 1
• Consider electromyography if radiculopathy or peripheral nerve compression is suspected; EMG may reveal extrapelvic sciatic nerve compression. 3

Imaging Strategy

• MRI of the lumbar spine if radiculopathy is suspected based on dermatomal distribution of symptoms. 4
• MRI or ultrasound of the pelvis/buttock to evaluate for deep gluteal syndrome, sciatic neuritis, and peri-neural pathology. 4
• Doppler ultrasound or CT angiography if vascular claudication is suspected with atherosclerotic risk factors. 6, 5

Common Pitfalls

• Do not assume lumbar canal stenosis seen on imaging is responsible for symptoms; stenosis may be asymptomatic and fortuitously associated. 5
• Do not rely solely on ABI to exclude vascular disease; hypogastric or gluteal artery stenosis may not reduce ABI. 5
• Do not overlook posterior femoral cutaneous nerve involvement in piriformis syndrome, which causes posterior thigh symptoms more frequently than leg/foot pain. 2
• Patients with piriformis syndrome are often evaluated by multiple physicians with prolonged diagnostic delays (average 32 months in one series). 3