Piriformis Syndrome: This condition is characterized by the compression of the sciatic nerve by the piriformis muscle, leading to numbness, tingling, and pain in the gluteal region and back. The intermittent nature of the symptoms and their location make piriformis syndrome a plausible explanation.

Lumbar Radiculopathy: Compression or irritation of the nerve roots in the lumbar spine can cause numbness, pain, and weakness in the lower back and gluteal area. The bilateral nature of the symptoms could suggest a more central or widespread issue in the lumbar spine.
Peripheral Neuropathy: Although more commonly associated with diabetes or other systemic conditions, peripheral neuropathy can cause numbness and tingling in various parts of the body, including the gluteal region, especially if the neuropathy affects the nerves supplying these areas.
Cauda Equina Syndrome: A less common condition where the nerves in the spinal canal are compressed, leading to symptoms such as numbness in the gluteal region, among other neurological deficits. The bilateral and intermittent nature of the symptoms might suggest an early or mild form of this condition.

Spinal Stenosis: A narrowing of the spinal canal that can cause compression of the spinal cord or nerve roots, leading to symptoms like numbness, weakness, and pain in the back and legs. Given the potential for serious neurological consequences if left untreated, spinal stenosis is a critical diagnosis not to miss.
Multiple Myeloma or Metastatic Cancer: Although less likely, these conditions can cause back pain and neurological symptoms due to compression of the spinal cord or nerve roots by tumors. Early detection is crucial for treatment and prognosis.
Infectious or Inflammatory Conditions (e.g., Abscess, Epidural Abscess): These conditions can cause severe back pain and neurological deficits, including numbness, and require immediate medical attention to prevent serious complications.

Tarlov Cysts: Abnormal fluid-filled sacs that can compress nerve roots, leading to a variety of neurological symptoms, including numbness in the gluteal region and back.
Arachnoiditis: Inflammation of the membranes surrounding the spinal cord, which can cause pain, numbness, and other neurological symptoms in the back and legs.
Neurosyphilis: A condition caused by the progression of syphilis to the nervous system, which can lead to a wide range of neurological symptoms, including numbness and back pain, although this would be less common and typically associated with other systemic symptoms.