Unilateral Cool Sensation on Left Buttock
The most likely cause of a constant cool-to-touch sensation localized to the left buttock is a peripheral nerve compression syndrome, specifically deep gluteal syndrome (formerly called piriformis syndrome) or cluneal nerve entrapment, which can cause altered sensation including temperature perception changes. 1, 2
Understanding the Symptom
Your description of a "cool to touch" sensation represents an altered temperature perception, which is a recognized manifestation of nerve dysfunction:
- Neuropathic sensory changes commonly include subjective sensations of altered temperature, such as feeling very warm or very cold in affected areas 3
- The buttock region is richly innervated by multiple nerves that can become entrapped, including the sciatic nerve, superior/inferior gluteal nerves, posterior cutaneous nerve of thigh, and cluneal nerves 2, 4
- Temperature sensation abnormalities indicate involvement of small nerve fibers that transmit thermal information 3
Most Likely Diagnoses
Deep Gluteal Syndrome (Sciatic Nerve Entrapment)
- Compression of the sciatic nerve in the subgluteal space is the primary pelvic cause of neural-mediated buttock symptoms 2
- Typical presentation includes buttock pain, sciatica, and altered sensation that worsens with prolonged sitting 1, 5
- Physical findings include tenderness in the sciatic notch and pain with hip flexion, adduction, and internal rotation (FADIR test) 5
- Anatomical variants of pelvic girdle muscles, muscle spasm, and functional factors contribute to nerve compression 2
Cluneal Nerve Entrapment
- Entrapment at the iliac crest can cause "pseudo-sciatica" with buttock symptoms 2
- This specifically affects the lateral buttock region and can cause altered sensation without typical sciatica 2
Diagnostic Approach
MRI of the lumbar spine without contrast is the recommended initial imaging if neurological symptoms are present 6:
- MRI can identify sciatic neuritis, peri-sciatic pathology, neural compression, and peri-neural adhesions or fibrosis 2
- Ultrasound can also visualize nerve pathology and guide therapeutic injections 1, 2
- Standard imaging is often normal in early nerve entrapment, making this primarily a clinical diagnosis 1, 5
Key clinical examination findings to assess:
- Tenderness over the sciatic notch or iliac crest 5
- Pain reproduction with FADIR maneuver (hip flexion, adduction, internal rotation) 1, 5
- Freiberg sign (pain with passive internal rotation) and Pace sign (pain with resisted abduction and external rotation) 1
- Direct palpation of the piriformis muscle reproducing symptoms 1
Initial Management Strategy
Conservative treatment should be initiated first 1, 5:
- Physical therapy focusing on stretching the piriformis and gluteal muscles to break the pain-spasm cycle 1, 5
- Activity modification to avoid prolonged sitting and positions that exacerbate symptoms 1, 5
- NSAIDs for pain management 1
For refractory cases:
- Ultrasound or imaging-guided corticosteroid injections into the piriformis or around the sciatic nerve 1, 2
- Botulinum toxin injections for persistent muscle spasm 1
- Surgical decompression (piriformis tenotomy, sciatic nerve decompression) only after failure of all conservative measures 1, 5
Important Caveats
- Vascular causes must be excluded if the coolness is objective (actually cooler temperature on palpation rather than just sensation), as this could indicate arterial insufficiency requiring urgent evaluation 3
- Lumbar spine pathology (disc herniation, spinal stenosis) can present similarly and should be ruled out with appropriate imaging 6
- Piriformis syndrome constitutes approximately 5% of cases of low back, buttock, and leg pain, making it an underrecognized but significant cause 5
- The term "deep gluteal syndrome" is now preferred over "piriformis syndrome" because multiple structures beyond just the piriformis muscle can cause sciatic nerve compression 2, 4