Keywords
spinal cord ischemia - delayed paraplegia
Spinal cord ischemia (SCI) is a rare, but serious complication of thoracic endovascular
aortic aneurysm repair (TEVAR) associated with debilitating paraplegia. Perfusion
of the spinal cord is normally maintained by a dynamic network of single segmental
arteries and collateral circulation comprised of the subclavian, intercostal, hypogastric,
and Adamkiewicz arteries.[1]
[2] In TEVAR, the obliteration of segmental branches can normally be compensated for
by adjacent uncovered collateral vessels.[3] Nevertheless, any disturbance to this tenuous blood supply may induce profound enough
hypoperfusion to precipitate SCI.[4]
TEVAR theoretically avoids several critical hemodynamic changes implicated in SCI
that occur during open repair, including aortic cross-clamping and reperfusion injury.[5] The likelihood of developing post-TEVAR SCI is lower than open repair but still
occurs at an incidence of 2 to 15%.[6] Furthermore, the risk of SCI is considered highest during the 30-day perioperative
period.[7] The extent of neurologic deficits associated with SCI ranges from mild paraparesis
with potential for recovery, all the way up to complete paralysis from irreversible
ischemia.
Compared with immediate SCI, which is observed shortly after emergence from anesthesia,
delayed-onset SCI is an underreported phenomenon that follows a period of normal neurologic
function and is considered secondary to a postoperative event. The timing of delayed-onset
SCI remains variable, with the literature describing occurrences from several weeks
up to 19 months postoperatively.[2]
[3]
[8]
[9]
[10] We present a rare case of delayed SCI occurring 20 months after TEVAR.
Case Review
The patient is a 65-year-old male with a history of hypertension, tobacco abuse, and
illicit drug use who presented with upper respiratory infection symptoms, chest and
back pain, and was found to have a Stanford Type A, DeBakey Type I aortic dissection
with 7-cm arch, and proximal descending aneurysm. Initial repair of the ascending
aorta was delayed due to cardiomyopathy attributed to methamphetamine abuse, respiratory
failure, pleural effusions, and acute kidney injury. Surgical repair was ultimately
delayed for 10 months to allow recovery. The first stage of repair was grafting of
the ascending aorta with elephant trunk into the descending aorta with separate grafts
from the ascending graft to the innominate, left carotid, and left subclavian arteries
([Fig. 1]). This procedure was done using cardiopulmonary bypass and hypothermic circulatory
arrest. The patient's postoperative course after the first stage was complicated by
pericardial effusion requiring a pericardial window and deep sternal infection requiring
debridement and removal of sternal hardware.
Fig. 1 Computed tomographic angiogram after repair of Type A dissection and prior to repair
of Type B aortic dissection. There is a stenosis at the graft to native aortic anastomosis
(blue arrow) and a stenosis at the junction of the graft to left subclavian artery
anastomosis (red arrow).
Five months later, the patient underwent the second stage of treatment with placement
of TEVAR stent grafts from the prior ascending graft to just above the celiac axis.
This procedure was technically challenging due to the anatomy of the elephant trunk,
narrowing of the brachiocephalic branch grafts as well as the graft-to-descending
aortic anastomosis, and dissection into the iliac arteries, which made cannulation
of the true lumen challenging. Ultimately, a brachiofemoral wire was needed, along
with angioplasty of the graft-to-aorta anastomosis, to introduce the TEVAR devices
([Fig. 2]). A lumbar drain was placed at the time of the procedure to reduce the risks of
neurologic injury. This drain was eventually removed on the third postoperative day.
Fig. 2 (A) Dilation of prior ascending aortic graft to aorta anastomotic stenosis with 16-mm
balloon. (B) Delivery of proximal thoracic endovascular aneurysm repair (TEVAR) device. (C) Balloon dilation of proximal TEVAR where it crosses the prior anastomotic stenosis.
(D) Final proximal TEVAR angiogram.
The patient was discharged home on the fifth postoperative day with near-normal renal
function and no evidence of paraplegia or paraparesis. A computed tomographic angiogram
(CTA) done 2 months after the second stage demonstrated excellent treatment of the
ascending and descending components of the dissection without endoleak. Persistent
filling of the false lumen was noted at the level of the distal thoracic aorta just
above the visceral segment of the aorta at the distal extent of the TEVAR.
The patient subsequently presented 20 months after the second stage procedure with
acute onset of paralysis. CTA done at the time of this presentation was largely unchanged
compared with the one at 2 months postoperatively except for interval and subtle false
lumen thrombosis noted in the distal thoracic aorta to the level of the renal arteries
([Fig. 3]). Visceral, renal, and hypogastric arteries remained patent. Subsequent evaluation,
including magnetic resonance imaging of the spine, concluded a complete loss of motor
and sensory function in both legs at the T10 level due to spinal cord infarction.
Fig. 3 (A) Postoperative computed tomographic angiogram (CTA) after thoracic endovascular aneurysm
repair (TEVAR) shows persistent patency of distal false lumen (blue arrow) 2 months
after procedure. (B) CTA at 20 months after repair at same level as in (A) showing interval thrombosis of false lumen (red arrow).
Discussion
SCI is a poorly understood and likely multifactorial complication of TEVAR. Hypotension,
thrombosis, embolization, decreased spinal cord perfusion, and elevated cerebrospinal
fluid (CSF) pressures are all patient-specific factors associated with increased risk
for SCI.[10]
[11]
[12]
[13] From a surgical standpoint, prior aortic aneurysm repair, length of stent coverage,
use of an iliofemoral conduit, and coverage of the left subclavian and hypogastric
arteries are all factors implicated for increased risk of SCI.[11]
[12]
[13]
[14] The pathogenesis of delayed post-TEVAR SCI is also rather unique, given that patency
of critical segmental arteries, covered by the stent graft, can be maintained not
only by native collateral circulation, but also by residual flow through the false
lumen.[15]
Multimodal strategies involving early recognition and rescue intervention are emerging
via SCI treatment algorithms. In 2021, the U.S. Aortic Research Consortium published
guidelines recommending placement of a CSF diversion device with drainage permitted
up to 30 mL/h, permissive hypertension to maintain mean arterial pressures (MAP) >90 mm
Hg, and maintaining hemoglobin levels ≥10 mg/dL in order to reduce SCI occurrence.[16] Other adjunctive strategies include naloxone to reduce spinal metabolism, distal
aortic perfusion, and intercostal artery reimplantation.[17]
[18]
[19] The ideal protocol for postoperative surveillance remains undefined; however, Tenorio
et al[20] recently published a low rate of 1% permanent paraplegia among 170 patients undergoing
fenestrated-branch endovascular aortic repair using a standardized preventative protocol
of multimodal interventions and follow-up with computed tomography and duplex ultrasound
of the renal-mesenteric arteries at 2, 6, 12 months and then annually thereafter during
the first 5 postoperative years.
This case report contributes to a sparse body of literature, describing delayed post-TEVAR
SCI at 20 months postoperatively.[10] Following complex two-stage reconstruction of his thoracic aorta, our patient's
postoperative recovery period did not reveal any immediate concerns for neurologic
deficits. His CSF drain was removed without issue on postoperative day 3 after he
was determined to have adequate hemodynamics, with MAP > 90 mm Hg and Hgb >10 g/L.
Follow-up CTA at 2 months postoperatively demonstrated a large amount of intraluminal
thrombus within the dissected aorta without endo leak, consistent with the intended
goals of therapy. He remained asymptomatic up to his 5-month telehealth appointment,
with intention to repeat his imaging at 6 months.
While it is unclear what triggered his delayed SCI at 20 months postoperatively, it
is possible that his remaining uncovered segmental branches had occluded following
false lumen thrombosis. Kelly et al[10] previously described the longest time elapsed between TEVAR and onset-of-neurologic
deficits at 19 months, with the authors also attributing their patient's delayed SCI
to false lumen thrombosis. In contrast to our patient, his spinal cord insult was
more diffuse and reversible and responded to intervention with spinal fluid drainage.
The potential impact of postoperative imaging surveillance in this delayed presentation
of neurologic insult is unknown, as the bulk of patients who develop interval false
lumen thrombosis do not develop an acute neurologic event. This scenario also runs
counterintuitive to conventional treatment goals, as false lumen thrombosis is generally
considered a desired outcome of TEVAR. Nevertheless, it is a reminder for the vascular
surgery community to maintain heightened vigilance for any potential contributing
factors of delayed post-TEVAR SCI on a case-by-case basis.
Conclusion
We describe an unusually delayed case of SCI at 20 months following TEVAR, with complete
paralysis of bilateral lower extremities attributed to false lumen thrombosis. This
experience highlights ongoing elusive challenges in the management of complex Type
B aortic dissection (TBAD), as the implicated cause of this patient's delayed paralysis
is contradictory to the standard goals of therapy. Although extremely uncommon, this
case highlights a devastating late outcome of management of complex TBAD, one with
limited options for successful treatment and reversal of the neurologic event.
