Clinical Reasoning: A 59-year-old woman with acute paraplegia
S. Prasad, MD,
R. S. Price, MD,
S. M. Kranick, MD,
J. H. Woo, MD,
R. W. Hurst, MD and
S. Galetta, MD
From the Departments of Neurology (S.P., R.S.P., S.M.K., S.G.) and Radiology (J.H.W., R.W.H.), Hospital of the University of Pennsylvania, Philadelphia.
Address correspondence and reprint requests to Dr. Sashank Prasad, Department of Neurology, Hospital of the University of Pennsylvania, 3 Gates Bldg., 3600 Spruce St., Philadelphia, PA 19104
Case presentation.
A 59-year-old woman with a history of hypertension developedacute bilateral flaccid leg weakness while watching television.She had shifted her weight while sitting on the couch and suddenlyfelt a sharp pain in her lower back and right leg. When shestood up to walk she noticed that her legs were numb; over thecourse of 1 hour she became unable to move her legs. She couldnot urinate voluntarily, and had dribbling incontinence. Shewas brought to the emergency department for evaluation.
Questions for consideration:
Where does acute paraplegia localize and what is the differentialdiagnosis?
What features of the history help make certainentities moreor less likely?
When evaluating a patient with acute bilateral leg weakness,the concern for a possible neurosurgical emergency requiresprompt diagnosis and treatment. The etiology can be consideredas one addresses the possible locations for the lesion. An anatomicapproach begins with the most central causes. A parasagittallesion in the brain, whether compressive or vascular, may causepredominant lower extremity dysfunction by involving the motorcortex bilaterally. A pontine lesion may cause leg weaknessthrough involvement of select corticospinal fibers. A spinalcord lesion at any level may cause isolated lower extremityweakness and sensory loss, since the lamination pattern of theascending and descending tracts places the leg fibers peripherallywhere they are vulnerable to external compressive lesions throughouttheir course. Another important location to consider is thecauda equina, which may be damaged by extrinsic compressionor by inflammatory and infiltrative processes. Acute demyelinatingradiculopathy and neuropathy, such as Guillain-Barrésyndrome, must be considered. Peripheral causes of weaknessinclude disorders of muscle or neuromuscular junction. Finally,psychogenic disorders such as conversion reaction must be considered,but only as a diagnosis of exclusion.
The constellation of bilateral leg weakness, radiating backpain, and overflow urinary incontinence suggests a lesion withinthe lower spinal cord or cauda equina. The presence of numbnessmakes a process involving muscle or neuromuscular junction untenable.The time course hints toward the possible etiology. The hyperacuteonset of her symptoms is concerning for a compressive or vascularetiology. An inflammatory process of the cord would typicallyhave a more subacute, escalating presentation.
In this patient, examination revealed complete paralysis ofthe legs proximally and distally, with the exception of 2/5left toe strength. Tone was diminished in the legs symmetrically,and normal in the arms. Sensation to light touch, vibration,pinprick, and temperature was absent below the umbilicus onthe right and decreased on the left. Joint position sense atthe toes was impaired bilaterally. Deep tendon reflexes wereabsent in the lower extremities and 2+ in the upper extremities.Plantar responses were extensor bilaterally. She had decreasedrectal tone. The remainder of the general and neurologic examinationwas unremarkable.
Questions for consideration:
How does the examination modify the differential, and help guidethe workup?
The pattern of severe lower extremity weakness, sensory loss,hyporeflexia, and extensor plantar responses is most consistentwith acute myelopathy. The likely location of the lesion isthe lower thoracic cord based on the sensory level at the umbilicus.Diminished sensation of temperature, vibration, and joint positionimplies involvement of both the anterolateral system and theposterior columns. Since these sensory tracts receive differentarterial blood supplies, the lesion extends beyond one arterialdistribution, which makes an isolated anterior spinal arteryinfarction less likely. By this reasoning, the most likely etiologyis extrinsic spinal cord compression or intramedullary hemorrhage.
Since spinal cord compression may be treatable with prompt neurosurgicalintervention, the first step in the evaluation of this patientis an emergent thoracic spine MRI (figure 1).
T2-weighted thoracic spine MRI, revealing central cord T2 hyperintensity from T4 to T8 (black arrow) and suggesting prominent flow voids within and on the surface of the cord (white arrow).
Although the MRI was technically limited due to motion degradation,it revealed central cord T2 hyperintensity from T4 to T8 andsuggested prominent flow voids within and on the surface ofthe cord. There was no significant cord expansion or evidenceof an extrinsic compressive process. In addition, there wasno intraparenchymal pathologic enhancement with gadolinium contrast.
Laboratory evaluations revealed an elevated white blood cellcount of 16.8 cells/dL with 89% neutrophils. Erythrocyte sedimentationrate was 19 mm/hour. The remainder of her blood cell counts,chemistries, and coagulation panels were within normal limits.
Question for consideration:
How do the MRI findings change the differential diagnosis andguide the diagnostic evaluation?
Central cord T2 hyperintensity is a nonspecific finding of intrinsicspinal cord damage that may be secondary to ischemia, inflammation,edema, hemorrhage, or traumatic injury. The absence of gadoliniumenhancement implies integrity of the blood–CNS barrierand makes an acute inflammatory lesion less likely.
Diffusion-weighted imaging of the spine did not demonstratean area of restricted diffusion. However, the sensitivity andspecificity of diffusion-weighted imaging in detecting spinalcord infarction are unclear. The results have a relatively poorsignal-to-noise ratio, with vulnerability to artifact from movement,breathing, and CSF flow.1
The prominent flow voids over the surface of the spinal cordraise the possibility of a vascular malformation, and requireadditional evaluation. Dynamic gadolinium-enhanced MR angiographymay localize an arteriovenous shunt when conventional MRI failsto do so.2 These images can be a useful adjunct in guiding theselective intercostal artery angiography needed to confirm thediagnosis of a spinal vascular malformation but often may notadequately differentiate between feeding arteries and drainingveins. Evaluation by catheter angiography, which precisely identifiesthe arterial supply and venous drainage of a malformation andalso allows assessment of potential treatment options, is thereforenecessary in cases where a spinal arteriovenous shunt lesionis suspected.
Gadolinium-enhanced spinal MR angiogram confirmed the presenceof prominent intradural, extramedullary veins, and suggestedan abnormal arterial-venous connection within the right T11/12intervertebral foramen, most consistent with a spinal-duralarteriovenous fistula (figure 2). MR angiography of the abdominaland thoracic aorta did not reveal a dissection.
Gadolinium-enhanced MR spinal angiography demonstrated dilated extramedullary vessels (A) and venous congestion (B), and also suggested an abnormal arterial-venous connection within the right T11/12 neural foramen (C).
Selective angiograms of the right and left segmental arteriesfrom T3 through L3 were obtained. The left L2 arteriogram demonstratedan intramedullary AVM at the T12-L1 level with arterial feedersarising from the hairpin loop of the radiculomedullary arteryof Adamkiewicz (figure 3; see video). The shared origin of thearterial feeders and the anterior spinal artery from the arteryof Adamkiewicz was confirmed on multiple oblique views. In addition,multiple dilated venous channels were seen extending to thelower thoracic levels. Venous drainage was into the inferiorvena cava at the right L1 level. No dural arteriovenous fistulawas identified. The remainder of the segmental arteries appearednormal. No arterial or venous aneurysms were seen.
Figure 3 Selective microcatheter left L2 arteriogram demonstrates an intramedullary arteriovenous malformation (AVM) (red arrow) at the T12-L1 level with arterial feeders arising from the artery of Adamkiewicz (black arrow)
Multiple dilated venous channels extend up to the lower thoracic level (blue arrow) and drain the AVM (blue arrowhead) into the inferior vena cava. See video.
These findings are consistent with a spinal intramedullary AVM,type 2 (glomus).
Treatment options were believed to be limited. The patient wasnot treated with arterial embolization or surgical interventionbecause the risk for either procedure was considered too significant.Embolization was not performed because the caliber of the arterialfeeder was too small for direct selective embolization of thefeeding vessels. Because the L2 radicular artery was shown tofeed the anterior spinal artery via the radiculomedullary arteryof Adamkiewicz, embolization of this branch would produce furthercord infarction. Surgery was not performed because the lesionwas inaccessible in its intramedullary location.
The patient remained stable, and after 1 week she was dischargedfor further rehabilitation. At 2-month follow-up, she had mademinimal recovery in her leg strength.
The blood supply to the spinal cord is provided by the singleanterior and dual posterior spinal arteries (figure 4). Fromthe anterior and posterior spinal arteries arise small sulcaland penetrating intramedullary arteries. The caliber of theanterior spinal artery narrows in the thoracic cord, resultingin greatly diminished descending blood flow.3 Blood flow tolower portions of the spinal cord arises from radiculomedullaryarteries that reconstitute the anterior spinal artery and radiculopialarteries that reconstitute the posterior spinal arteries.3 Radiculomedullaryand radiculopial arteries originate from radicular arteries.Thirty-one pairs of radicular arteries pass through the intervertebralforamina to supply each spinal nerve and the dura. They originatefrom large segmental arteries, which include the ascending cervical,deep cervical, vertebral, intercostal, lumbar, and sacral arteries.Only 6 to 10 radicular arteries give rise to radiculomedullarybranches, but the exact number and anatomic location is quitevariable.4 Of the radiculomedullary arteries supplying the lumbarcord, the largest is named the artery of Adamkiewicz.4
Note that the blood supply to the anterior spinal artery is reconstituted by the artery of Adamkiewicz. Courtesy Paul Schiffmacher.
The venous anatomy of the spinal cord includes intramedullaryveins that collect into the anterior and posterior superficialveins, which drain into radicular veins. Anterior and posteriorradicular veins drain into the epidural (or internal vertebral)venous plexus. The venous plexus drains into thoracic, abdominal,and intercostals veins.4 Of note, the venous drainage of thespinal cord does not contain valves, and under pathophysiologicconditions flow may become retrograde.
There are several types of spinal cord vascular malformations,each defined by its anatomic characteristics (table). Theseinclude the dural arteriovenous fistula (type 1 spinal duralAV fistula), intramedullary arteriovenous malformations (glomusor type 2 spinal cord AVM, and juvenile or type 3 spinal cordAVM), and direct perimedullary fistulas (type 4 spinal cordAV fistula).5 Other spinal cord vascular malformations, thediscussion of which is beyond the scope of this report, includecavernomas, telangiectasias, venous angiomas, epidural AVMs,paravertebral vascular malformations, vertebral hemangiomas,and complex syndromic vascular malformations, including Cobbmetameric angiomatosis and Osler-Weber-Rendu disseminated angiodysplasia.5
Table Characteristics of the different types of pathologic spinal arteriovenous connections
Glomus (type 2) spinal AVMs are intramedullary lesions, whichcontain intervening cord parenchyma within the abnormal tangledvessels.5 In the glomus AVM, the vascular nidus is compact.5The arterial supply is through an enlarged radiculomedullaryartery that also supplies the cord via anterior or posteriorspinal arteries. There is high flow through the lesion, as demonstratedby angiographic transit times.6 Drainage occurs by shunted anterogradeflow through engorged medullary spinal veins and the epiduralvenous plexus. These lesions can occur anywhere in the cord.6They typically affect younger patients, and are thought to resultfrom defective vascular embryogenesis.
The pathophysiology of acute decompensation in intramedullaryAVMs is likely related to intraparenchymal or subarachnoid hemorrhage,venous hypertension, or local ischemia. High-pressure turbulentblood flow predisposes to local arterial and venous aneurysms,which are vulnerable to rupture and cause hemorrhage.7 Alternatively,if there is sufficient shunting of blood through the high-flowAVM away from the cord parenchyma, cord ischemia may result.6More recently, venous congestion has been emphasized as an additionalinciting factor in the pathophysiology of some spinal intramedullaryAVMs.8 Indeed, our patient had evidence of extensive MRI cordsignal abnormality and diffuse angiographic venous engorgementsuggesting chronic venous hypertension. Although these potentialpathophysiologic mechanisms have each received support in theliterature, definitive evidence for any particular mechanismis lacking. In most cases there is likely a combination of underlyingpathophysiologic mechanisms.
Type 2 intramedullary AVMs can occasionally be treated withsurgical disconnection or resection, but the risk of poor outcomemay be substantial, depending on the location and extent ofthe lesion.6,9 In some cases, embolization of an intramedullaryAVM can be successful, depending on the anatomic characteristicsof the lesion and the results of test occlusion of the parentvessel.10
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