55‐YEAR‐OLD FEMALE WITH LOW BACK PAIN

CLINICAL HISTORY AND IMAGING

A 55‐year‐old female presented with low back pain radiating to her left leg. The pain started several years ago, and recently getting worse. The intermittent pain had a shooting quality that usually worsened after lying supine for a long time. She denied any bowel or bladder symptoms. Her past medical history and family history was unremarkable. Her physical exam was normal except for left lower extremity was 4+/5 for knee and ankle extension/flexion. She also had mild decreased light‐touch sensation in the left L4 and L5 distribution with 2‐beat clonus in her left leg. Her big toe was equivocal on the left and downgoing on the right.

Magnetic resonance imaging (MRI) of the spinal cord revealed multiple homogeneously enhancing, intradural, extramedullary lesions in the lumbar spine (Figure 1A) with the largest one located near the L5/S1 disc space. MRI of the brain as well as cervical and thoracic spine did not reveal any additional lesions. Computed Tomography of the chest, abdomen, and pelvis did not reveal occult malignancy. As the etiology of these lesions was not clear, the patient underwent a L5/S1 laminectomy, intra‐dural exploration, and biopsy of the largest lesion.

Figure 1.

GROSS AND MICROSCOPIC PATHOLOGY

Intra‐operatively, the lesion appeared creamy white in color and rubber‐like in texture and was associated with several nerve roots. Frozen and permanent specimens were sent to pathology, with a preliminary reading of spindle cell tumor. Nerve‐root stimulation and evoked potentials indicated the lesion was associated with nerves involved in motor and anal sphincter function. The patient recovered well from the surgery with stable neurological function.

Pathologic examination of the specimen revealed tumor as shown in Figures 1B and 1C. The tumor cells were strongly S100 positive, and were negative for epithelial membrane antigen. What is your diagnosis?

DIAGNOSIS

Intradural schwannoma in Schwannomatosis

DISCUSSION

Schwannomas are benign neoplasms of the peripheral nerve sheath that originate from the proliferation of Schwann cells and are typically well demarcated from surrounding tissue. Schwannomatosis has recently been recognized as a distinct tumor syndrome separate from NF‐1 or NF‐2 1, 7, 8, 9, 10. It is characterized by the presence of multiple schwannomas or Schwann cell hyperplasia without the cutaneous stigmata, neurofibromas, or vestibular schwannomas 6, 12. The dominant symptom is pain, which develops as an schwannoma enlarges, compresses nerves, or presses on adjacent tissue. Recent advances in medical genetics suggest inactivation of both SMARCB1 and NF2 genes could explain the cause of schwannomatosis 2, 3, 11.

The typical locations of schwannomas include spinal nerves, peripheral nerves, and multiple cranial nerves. Isolated involvement of a single limb (4) or a single nerve (5) by multiple schwannomas have also been reported. Here we report a case of schwannomatosis with multiple intradural, extramedullary lesions causing radiculopathy.

The goal of surgery is to obtain a diagnosis as well to remove symptomatic lesions as possible if clinical symptoms appear referable to a specific lesion. Complete surgical resection is generally not undertaken given the presence of multiple lesions throughout the spinal cord and/or cauda equina. Treatments for progressive lesions primarily include re‐resection and radiation. Given her stable examination at present, this patient will undergo observation and be referred to medical genetics for further work‐up.