Case #06 Discussion:

Case History:

15 y/o who was injured 7 months ago while playing basketball. He has had no difficulties in the interim period until recently when he developed severe low back pain that radiated down his posterior thigh. He has also noted some right leg weakness, as well as intermittent numbness along his posterior thigh. He denies bowel or bladder dysfunction, weight loss, or fevers.

He has no significant PMH. He denies drug allergies or tobacco use. His family history is remarkable only for a maternal grandmother who had surgery at age 65 for removal of spine tumors (diagnosis unavailable).

On physical exam, he is a young, muscular male in NAD. He has full lumbar ROM; however, with right bending he experiences pain that radiates posteriorly and laterally down his right leg to the knee, as well as right sacroiliac pain. Supine leg raising on the right elicits pain in a similar distribution that is immediately diminished by knee flexion, and femoral stretch on the right side causes severe right sacroiliac pain. He has a slight weakness of hip flexion on the right side (5-/5); however, his sensory exam and deep tendon reflexes are completely normal. Erythrocyte sedimentation rate (ESR) = 9.

What is the differential diagnosis for the back/leg pain?

Several clues in the history and physical exam assist in assigning and ranking diagnostic possibilities:

(1) This patient has pain that is consistent with an L5-SI radicular distribution (posterolateral thigh). It is also possible that his pain is "pseudoradicular," i.e. referred pain. The former possibility is supported by the severity of his leg pain and the fact that it is immediately elicited by the straight leg raising (SLR) test and just as rapidly alleviated by knee bending, as well as by the slight weakening of hip flexion on the right (iliopsoas). Of course, both types of pain may coexist.

The possibility of lumbosacral and/or sacroiliac muscular strain secondary to injury must be considered in any case of acute-onset pain that involves the sacroiliac joint and radiates to the posterior thigh. Herniation of a lumbar intervertebral disc resulting in nerve compression is a common cause of radicular pain, although it mainly occurs in individuals in their fourth and fifth decades of life. Likewise, facet joint hypertrophy, a less common cause of radicular pain that produces a positive SLR test with variable sensory, motor and reflex deficits, typically occurs in middle-age. Additional etiologies of low back pain and/or sacroiliac pain include ankylosing spondylitis (common in young men), and juvenile rheumatoid arthritis; however, these chronic inflammatory conditions are usually associated with an elevated ESR. Other causes of pediatric back pain are infectious meningitis, tuberculosis spondylitis, and herpes zoster; however, his lack of fever points away from an infectious process.

(2) This patient has had a prior trauma that was associated with back pain, albeit 7 months ago, thus it is reasonable to consider his current state in the context of possible sequelae. Indeed, traumatic injuries constitute the most frequent cause of low back pain.

Although his initial trauma was not very severe, one must consider the possibility of traumatic vertebral fracture, usually the result of flexion injuries. These occur in the form of fracture dislocations, vertebral compression fractures, or, in more severe injuries, a "bursting" fracture of a vertebral body +/- associated fracture of a pedicle, lamina, or spinous process. Translocation Fractures are relatively common, although these predominate at the thoracolumbar junction and are often accompanied by a high incidence of neurological deficit. Against a diagnosis of fracture stands the long asymptomatic interim period between his fall and the onset of his current complaint.

A complete differential for post-traumatic radicular pain would also include hematoma causing disc compression, although the long interim period free of symptoms also puts this fairly low on the differential. Furthermore, although primary osteoarthritis largely occurs in older individuals, osteoarthritis and spondylolysis can occur secondary to trauma and should be considered. Bilateral spondylolysis can result in spondylolisthesis, anterior translocation of a vertebrae relative to an inferior one, which is most commonly seen at the L5-S1 junction. Likewise, spinal stenosis can also follow trauma, and symptoms include back and leg pain induced by walking or standing. A more distant possibility might be post-traumatic lumbar adhesive arachnoiditis, a fibrotic process that can follow an inflammatory response to local tissue injury in the subarachnoid space, although it is most commonly seen postsurgically. Finally, delayed vertebral collapse (Kummel's disease) is a rare phenomenon that may reflect osteonecrosis of a vertebral body as a result of vascular injury but has also been attributed to nutritional, traumatic, neurologic, and vasomotor etiologies. Collapse of the injured vertebrae may occur over a period of six weeks or more. The paucity of sensory and motor deficiencies point away from spinal cord involvement in this case, and the intact bladder and bowel function suggest that the cauda equina is not involved.

(3) This patient has a maternal grandmother with a history of spine tumors of unknown etiology necessitating surgery at age 65. This raises the possibility that he has some hereditary syndrome involving a benign or malignant tumor that impinges on his L5-S1 nerve root. In this case, it is possible that he has sustained a pathologic fracture. Neoplasms of the spinal cord include extramedullary (epidural or intradural) or intramedullary forms. While adults are most likely to suffer metastatic epidural neoplasms, the pediatric population more commonly develops primary CNS tumors such as schwannomas, neurofibromas, and meningiomas. A.B. has a combination of radicular symptoms with a relative paucity of neurologic signs, therefore discussion will focus on extramedullary tumors that may cause nerve root compression by impingement. Schwannomas and neurofibromas are nerve sheath tumors and may be intra- or epidural in location. Schwannomas and neurofibromas arise from nerve roots and cause symptoms by compression rather than destruction of the nerve root. Unlike schwannomas, neurofibromas contain nerve elements and are encapsulated. Both schwannomas and spinal neurofibromas are associated with the hereditary syndrome neurofibromatosis, type 1; however, A.B does not possess the characteristic skin lesions seen with this hereditary syndrome. Ganglioneuromas are benign tumors found in adolescents and young adults that arise from the sympathetic ganglia and can sometimes be distinguished by production of catecholamines and by internal calcification. Meningiomas, the most common intradural tumors are another possibility, although they are more frequent in the thoracic than in the lumbar cord and tend to occur in middle-aged women. Together meningiomas and schwannomas comprise more than half of intraspinal tumors, therefore both must be fairly high on the differential

When considering neoplastic processes producing back pain, one should include extension of a retroperitoneal tumor in the differential. Neuroblastomas and related tumors arising from paraspinous neural remnants may infiltrate through the neural foramina and compress nerve roots and/or spinal cord; however, these occur almost exclusively in children under the age of five. Other possible paraspinal masses in a teen-aged male include a primary lymphoma, a primary germ cell tumor, and metastatic disease to retroperitoneal lymph nodes originating from testicular cancer. Indeed, in males ages 15-34, lymphoma is second only to leukemia as a leading cause of primary tumors in patients dying of cancer.

What is the simplest, cheapest radiologic test you could perform to assess the possibility of fracture? What should you look for?

The simplest, cheapest radiologic test for low back pain in the setting of trauma is the plain radiograph. In the setting of trauma, this would be an appropriate first test in order to assess the presence and stability of a fracture. Fractures involving the anterior column (longitudinal ligament and the anterior vertebral body) are relatively stable, whereas middle column (middle-vertebral body to posterior vertebral body including posterior longitudinal ligament) and/or posterior column (pedicles, facets, spinous processes and all associated ligaments), as well as those involving all three columns, are considered unstable

Compression fractures are the most common type of lumbar fracture and often involve only the anterior vertebral body. These are best appreciated on the lateral view as a wedge deformity, although interpedunculate widening on the AP view indicates a more severe (posterior) fracture. Translocation fractures are usually seen at the thoracolumbar j unction-- lateral radiograph demonstrates anterior translocation of the upper vertebrae with respect to the lower vertebrae, and the AP view shows widening of the interspinous distance and possibly rotational malalignment. Burst fractures involve compression of the vertebra and intervertebral disc in a manner that results in herniation of the compressed disc into the vertebral body causing the vertebra to fracture outward producing anterior and posterior fracture lines. Burst fractures may be difficult to distinguish from compression fractures on plain radiograph; however, they are more likely to involve posterior elements, and fractures of the pedicles and laminae or dislocations of the facets may be seen.

AP and lateral radiographs in this case revealed only a slight narrowing of the pars interarticularis of the lowest lumbar vertebrae (L5) and a suggestion of left spondylolysis.

What other test(s) would be helpful in this case? Is there any advantage to CT over MRI, or vice versa?

CT scan would be helpful to confirm the finding of L5 spondylolysis and to visualize any associated disc disease. CT is superior to MRI in visualizing spondylolysis-- otherwise the two are equivalent. In the case of a fracture, CT is appropriate to evaluate degree of canal compromise and the presence of retropulsed fragments that may involve the spinal cord and/or nerve roots. CT scan should include at least one segment above and one below the suspected injury.

Vertebral damage following a relatively mild trauma raises the question of pathologic fracture, especially in a case where the patient has a family history of "spine tumors." MRI has some advantages over CT for investigating pathologic fractures due to its superior ability to discriminate soft tissue structures, particularly the spinal cord, and the capability of imaging in multiple dimensions. In addition, MRI does not involve ionizing radiation.

How might one obtain a sample of the paraspinal mass for histological analysis?

Both ultrasound and CT imaging are used to direct needle biopsies of suspicious masses. In this case CT is a better choice due to the proximity of the lesion to the bony vertebrae, which may obstruct ultrasound visualization. CT will also provide better visualization of the spinal cord and nerve roots to avoid damaging these structures.

First, 3 mm contiguous axial images taken from T7/T8 to T9/T10 to assess the best approach to the lesion CT and radio-opaque markers placed on the skin marking the best entry site. Axial images were again taken to confirm accurate placement of the biopsy needle and fine needle aspiration (FNA) was followed by core biopsy.

Outcome

Histopathological analysis of the FNA revealed atypical lymphocytic cells consistent with malignant lymphoma.