Spinal shock

A 60-year-old woman with a medical history of chronic lower back pain presented with a chief complaint that she could not walk. After swimming, she had a "funny feeling" in her lower back, felt a need to defecate, went to the commode, and developed numbness and the inability to move her legs. She reported no recent trauma, illness, or exacerbation of her back pain. Physical examination showed flaccid paralysis in both lower extremities, decreased rectal tone, absent reflexes, and absent sensation, including touch, temperature, vibration, and proprioception below the T12 level. The results of a lumbar puncture were negative for malignancy, infection, and inflammation. No oligoclonal bands were identified. A computed tomographic scan of the brain was negative. A magnetic resonance image of the spine showed increased T2-weighted signal within the thoracic spine from T9 through T11 without associated enhancement or cord enlargement, consistent with acute infarction (Figure 1, arrow). Degenerative changes of the vertebral end plates were noted at L3 through L4 and L4 through L5, and a Schmorl node was identified on the superior end plate of L4. No evidence of a spinal arteriovenous fistula was seen. The results of serum chemical analysis and an autoimmune workup were unremarkable. The results of a VDRL test and rapid plasma reagin were negative. No source of emboli could be found on echocardiogram or carotid ultrasound. During a 7-day hospital admission, she regained little motor function in her lower extremities, had no bowel or bladder function, and had slight recovery of vibration sensation. She was then discharged to a rehabilitation facility. Seventeen days later she died suddenly.

Postmortem examination showed a massive saddle pulmonary embolus. The heart was unremarkable, and no atherosclerosis was seen in the aorta. A small leiomyoma was seen in the uterus. Grossly, the upper lumbar spinal cord showed anterior and lateral softening and discoloration (Figure 2). Histologic examination confirmed the presence of subacute spinal cord infarction in the distribution of the anterior spinal artery. An immunostain for glial fibrillary acidic protein highlights preserved spinal cord surrounding the infarct (Figure 3, arrow). Several pink-gray emboli were seen in subarachnoid arterioles (Figure 4, hematoxylin-eosin). These emboli stained reddish purple on periodic acid-Schiff and blue on Masson trichrome histochemical stains.

What is your diagnosis?

Pathologic Diagnosis: Spinal Cord Infarction Secondary to Fibrocartilaginous (Intervertebral Disk) Embolism

Spinal cord infarction typically involves the distribution of the anterior spinal artery and is commonly due to occlusive lesions and/or hypotension, with atherosclerosis being the most common cause.1 Other causes include trauma, acute myelitis, multiple sclerosis, compressive lesions, tumors, syphilitic arteritis, spontaneous thrombosis of the anterior spinal artery, dissecting aortic aneurysm, hematomyelia, iatrogenic injury, and emboli. The source of emboli includes atheromatous material, bacterial endocarditis, atrial myxoma, caisson disease (decompression sickness), and intervertebral disk embolization. Infarction of the anterior spinal artery distribution produces a syndrome characterized by abrupt radicular or diffuse pain, flaccid paralysis, loss of distal pain and temperature sensation, and loss of sphincter control; usually there is sparing of the posterior columns with preservation of proprioception and vibration sensation.1

Spinal cord infarction due to an embolus of intervertebral disk material is a rare but well-documented event.2-9 Approximately 40 cases of fibrocartilaginous embolism from intervertebral disk tissue have been reported in patients who range in ages from 6 to 77 years.9 Most of these cases were diagnosed at autopsy.6,8

The location of embolization is the cervical spinal cord in approximately 70% of cases and the lumbar cord in the remainder; the entire spinal cord is rarely involved.8 Cervical emboli may involve the medulla or upper thoracic cord. Lumbar emboli commonly involve thoracic and/or sacral segments as well. The emboli are located within arteries in approximately two thirds of cases.8 Both arterial and venous involvement is seen in approximately 25% of cases, and emboli are rarely found only within veins.

No precipitating injury or factor can be found in approximately half of the cases,7,8 and a history of minor trauma is seen in approximately 20% of the cases. Symptoms may initiate on awakening or after a Valsalva-like maneuver, such as straining to defecate. Other less frequently reported associations include a history of low back pain, motor vehicle crash, vertebral body fracture, lower back disk surgery, oral contraceptive use, pregnancy, obesity, and extended steroid therapy.7,8

A typical clinical history with fibrocartilaginous embolism is acute onset of pain in the neck or lower back followed minutes to hours later by quadriplegia or paraplegia in cervical and lumbar cases, respectively.7,8 Spinal shock with abolishment of reflexes and sphincter tone follows soon thereafter. Cervical involvement can lead to respiratory depression. Death follows relatively rapidly from respiratory compromise in cervical cases, with a mean survival of 12 days.7 A fatal outcome following lumbar emboli is secondary to pulmonary emboli or sepsis. Significant neurologic recovery is distinctly uncommon.8

Toro et al7 summarized the spinal cord histopathologic lesions following embolization. If death ensues within hours, multiple microscopic hemorrhages may be seen within the affected spinal cord segments, often localized to the gray matter. After a couple of days, red neurons may be seen. Within a week, necrosis, macrophages, gliosis, and capillary proliferation can be expected. With extended survival, the spinal cord pathologic findings will consist of cavitation and gliosis.

The diagnosis of fibrocartilaginous emboli is made by documenting the presence of intervertebral disk material within the spinal cord vasculature. Examination of multiple levels of the spinal cord may be necessary to find the emboli. Fibrocartilage has the following histochemical staining properties: purple on periodic acid-Schiff, blue on Masson trichrome, red with mucicarmine, blue with Alcian blue, green with Gomori trichrome for elastic fibers, and strong metachromatic purple on cresyl-violet, thionine, and toluidine blue.3,7

Several theories attempt to explain the pathogenesis of fibrocartilaginous emboli. One theory is that as the nucleus pulposus herniates, it may lacerate and enter a radicular artery.2 Another theory is that disk material may herniate through the vertebral end plate into vertebral bone marrow to form what are known as Schmorl nodes.10 The fibrocartilage in the marrow may then drain from marrow sinuses into valveless perispinal veins, where they may be driven into the spinal leptomeningeal veins during times of increased pressure, such as a Valsalva maneuver.3 Arteriovenous anastomoses would act as a conduit to allow passage of the emboli into the arterial circulation.4,5 Significantly increased and sustained pressure may even drive fibrocartilage from the marrow sinuses directly into arteries.8 A final theory addresses the embryologic vascular supply of the nucleus pulposus that is lost during childhood. Direct injection of fibrocartilage into these vessels during episodes of increased pressure, with retrograde travel into a radicular artery, may explain emboli seen in younger patients.,2,9

References

1. Sandson TA, Friedman JH. Spinal cord infarction: report of 8 cases and review of the literature. Medicine. 1989;68:282-292.

2. Naiman JL, Donohue WL, Prichard JS. Fatal nucleus pulposus embolism of spinal cord after trauma. Neurology. 1961;11:83-87.

3. Feigin I, Popoff N, Adachi M. Fibrocartilaginous venous emboli to the spinal cord with necrotic myelopathy. J Neuropathol Exp Neurol. 1965;24:63-74.

4. Srigley JR, Lambert CD, Bilbao JM, et al. Spinal cord infarction secondary to intervertebral disc embolism. Ann Neurol. 1981;9:296-301.

5. Kepes JJ, Reynard JD. Infarction of spinal cord and medulla oblongata caused by fibrocartilaginous emboli: report of a case. Virchows Arch A Pathol Palhol Anal. 1973;361:185-193.

6. Mikulis DJ, Ogilvy CS, McKee A, et al. Spinal cord infarction and fibrocartilagenous emboli. Am J Neuroradiol. 1992;13:155-160.

7. Toro G, Roman GC, Navarro-Roman L, et al. Natural history of spinal cord infarction caused by nucleus pulposus embolism. Spine. 1994;19:360-366.

8. Tosi L, Rigoli C, Beltramello A. Fibrocartilaginous embolism of the spinal cord: a clinical and pathogenetic reconsideration. J Neurol Neurosurg Psychiatry. 1996;60:55-60.

9. Davis GA, Klug GL. Acute-onset nontraumatic paraplegia in childhood: fibrocartilaginous embolism or acute myelitis? Childs Nerv Syst. 2000;16:551-554.

10. McFadden KD, Taylor JR. End-plate lesions of the lumbar spine. Spine. 1989;14:867-869.

Russell T. Alexander, MD; Thomas J. Cummings, MD

Accepted for publication January 14, 2003.

From the Department of Pathology, Duke University Medical Center, Durham, NC.

Corresponding author: Russell T. Alexander, MD, Department of Pathology, Duke University Medical Center, DUMC Box 3712, Durham, NC 27710 (e-mail rusty4i@yahoo.com).

Reprints not available from the authors.

Copyright College of American Pathologists Aug 2003
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