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Vol 9, No 2, March/April 2001
137
Neurologic complications after lum-
bar spine surgery may be broadly
classified by the mechanism of
injury and by the time period dur-
ing which they occur. The causes of
injury are generally either indirect
or direct, with the latter including
laceration, compression, traction,
and avulsion injuries to the neural
elements. Such direct causes are
most commonly the result of a tech-
nical mishap by the surgeon. In-
direct injuries are due to the disrup-
tion of the blood supply to the
spinal cord and nerve roots or to the
gradual compression of the neural
elements, as by correction of defor-
mity or by a postoperative hema-
toma. This type of injury is usually
the result of ischemia or the disrup-
tion of axoplasmic flow, which pro-
vides neural nutrition. Its causes
are more difficult to define and are
often inexplicable.
Neurologic injuries categorized
by the time period during which
the insult occurs may be intraoper-
ative, early postoperative (1 to 14
days), or delayed postoperative

(after 14 days) events. Intraopera-
tive events are generally related to
complications arising from anes-
thesia, patient positioning, surgical
technique, or procedure-specific
risks. Early in the postoperative
period and up to 2 weeks after sur-
gery, neurologic injuries are most
commonly secondary to direct
compression of the neural ele-
ments. This is often caused by the
mass effect of postoperative hema-
toma, pseudomeningoceles, and
epidural abscesses. After partial
diskectomy, retained fragments or
recurrent herniations may also
cause neurologic symptoms in this
time period. After 14 days from
surgery, recurrent disk herniation
should be considered more likely,
although this may occur earlier
as well.
To both minimize and prevent
potential neurologic complications
that may occur in association with
lumbar spine surgery, the surgeon
must thoroughly understand the
relevant anatomy and must do
meticulous preoperative planning.
Additionally, a thorough under-

standing of the etiology of the com-
plications can decrease their inci-
dence. When complications do
occur, rapid recognition and appro-
priate treatment can minimize their
effect.
Anatomy
Knowledge of the relevant anatomy
is essential to minimizing direct
neural injuries. The spinal cord ter-
minates as the conus medullaris at
the level of the inferior border of L1
and the superior border of L2.
Spinal cord tissue is much less tol-
erant of traction and compression
than the nerve roots are. Even
minimal manipulation of the cord
may cause profound neurologic
consequences. Focal injury to the
conus medullaris can cause injury
to the function of the lower sacral
roots and result in disturbances in
bowel, bladder, or sexual function
with or without other obvious neu-
rologic deficits in the lower extrem-
ities.
Dr. Antonacci is Assistant Professor of
Orthopaedic Surgery and Director, Spine
Diagnostic and Treatment Center, MCP
Hahnemann University School of Medicine,

Philadelphia, Pa. Dr. Eismont is Professor of
Orthopaedic Surgery, University of Miami
School of Medicine, Miami, Fla.
Reprint requests: Dr. Antonacci, Spine
Diagnostic and Treatment Center, Graduate
Hospital, 1800 Lombard Street, Philadelphia,
PA 19103.
Copyright 2001 by the American Academy of
Orthopaedic Surgeons.
Abstract
With the increasing complexity and number of lumbar spine operations being
performed, the potential number of patients who will sustain perioperative com-
plications, including those that involve neural structures, has also increased.
Neurologic complications after lumbar spine surgery can be categorized by the
perioperative time period during which they occur and by their mechanism of
injury. Although the overall incidence of neurologic complications after lumbar
surgery is low, the severity of these injuries mandates careful preoperative plan-
ning, awareness of risk, and meticulous attention to perioperative details.
J Am Acad Orthop Surg 2001;9:137-145
Neurologic Complications After Lumbar Spine Surgery
M. Darryl Antonacci, MD, and Frank J. Eismont, MD
The spinal nerve roots, while
more tolerant of mechanical defor-
mation than the spinal cord, are less
tolerant than the peripheral nerves.
The intradural nerve rootlets are
covered by only a thin membra-
nous root sheath, which is perme-
able to cerebral spinal fluid for nu-
trition.

1
In contrast, peripheral
nerves are protected by an epineu-
rium and a perineurium. This, in
addition to a more developed con-
nective tissue layer, makes periph-
eral nerves much less susceptible to
injury than the intrathecal nerve
rootlets.
The results of experimental stud-
ies in dogs suggest that when the
thecal sac is compressed acutely to
45% of its normal area (i.e., to ap-
proximately 75 of the normal 170
mm
2
), significant nerve-root com-
pression occurs, with measurable
changes in both motor and sensory
function.
2
The motor nerve roots
recover more quickly than the sen-
sory roots after the pressure is re-
leased; thus, transient compression
is more likely to affect the sensory
roots. The critical value of 75 mm
2
can be used for the radiologic diag-
nosis of central spinal stenosis. Re-

ducing the cross-sectional area of the
thecal sac to approximately 65 mm
2
generates a pressure level of about
50 mm Hg in the cauda equina.
Measurable changes in spinal nerve-
root conduction generally occur
between 50 and 75 mm Hg.
3
The
effects of compression are related
not only to the duration of compres-
sion and the pressure itself but also
to the rate of onset.
4
In the acute
injury setting, rapid application of
compression to the nerve roots
causes more pronounced tissue
changes than slow application. The
application of pressure over multi-
ple spinal levels and the combina-
tion of compression with systemic
hypotension can lower these thresh-
old injury levels.
The pedicle is a constant anatomic
landmark that can be used to locate
the exiting nerve root and thus min-
imize the likelihood of inadvertent
injury to it. If the anatomy is aber-

rant, the one constant is the relation-
ship of the pedicle to the nerve root,
which lies along the inferomedial
edge of the pedicle. In cases with
poor visualization of the nerve root,
resection of bone until the pedicle is
visible will aid in the identification
of the exiting nerve root.
During anterior lumbar surgery,
the hypogastric nerve plexus and
sympathetic chain are at risk of
injury. The aorta, the vena cava,
and collateral vessels are preverte-
bral and in close proximity to the
hypogastric nerve plexus. This
nerve plexus is approximately 6 to
8 cm in length along the surface of
the aorta and extends from the
cephalad aspect of L4 (as the supe-
rior hypogastric plexus) to the first
sacral vertebra. As the plexus en-
ters the pelvis, it divides into right
and left divisions, which course dis-
tally and join the inferior hypogas-
tric plexus. These fibers innervate
the seminal vesicles and vas deferens
in the male; injury to these struc-
tures can lead to retrograde ejacu-
lation. Injury to the hypogastric
plexus in approaches to the L5-S1

disk space is minimized by blunt
dissection directly on the anterior
surface of the disk. Sweeping the
prevertebral tissues and hypogas-
tric nerve plexus laterally, rather
than dissecting through these struc-
tures, decreases the risk of injury to
the nerve fibers. The use of bipolar
cautery and limited exposure also
helps to minimize the risk of injury.
The exposure of upper lumbar seg-
ments is not associated with as
high a risk for retrograde ejacula-
tion as the exposure of L5-S1, be-
cause the sympathetic fibers in-
volved lie on the anterior aortic
wall. Injury to the sympathetic
chain, which lies along the anterior
border of the psoas muscle, can
manifest as patient complaints of
contralateral foot coldness. In fact,
vasodilatation secondary to this in-
jury causes increased warmth in the
ipsilateral foot.
Preoperative Planning
Failure to recognize variations in
normal anatomy on preoperative
studies may predispose to injury
(e.g., asymptomatic spina bifida).
Such a finding may necessitate a

particularly careful dissection or
alteration in surgical approach.
Similar caution is necessary after
prior laminectomies or with wid-
ened interlaminar spaces. It is
good practice to review all preop-
erative radiographs just prior to
surgery, with special attention to
the variant anatomy in each indi-
vidual case.
In other situations, such as in
patients with high-grade lumbar or
cervical stenosis, preoperative con-
sideration of patient positioning
may help avoid unexpected injury.
For example, patients with cervical
stenosis should be carefully trans-
ferred to the prone position with
their heads in a neutral or slightly
flexed position, or awake position-
ing should be used. In severe cases,
consideration should also be given
to fiberoptic intubation. In patients
with high-grade lumbar spinal
stenosis, use of large Kerrison ron-
geurs should be avoided in favor of
the motorized diamond burr. Un-
der these conditions, placement of
cottonoid pledgets within a tightly
narrowed epidural space should be

avoided.
Prior to surgery, patients should
be instructed to discontinue the use
of anti-inflammatory medications
(for 2 to 3 days) and aspirin (for 2 to
10 days) to minimize intraoperative
and postoperative blood loss. Pa-
tients should also be questioned
about complementary or alternative
medications, such as gingko and
cayenne, which can have effects on
clotting.
Neurologic Complications After Lumbar Spine Surgery
Journal of the American Academy of Orthopaedic Surgeons
138
Complications Related to
Induction of Anesthesia
and Patient Positioning
The risk of intraoperative neuro-
logic injuries begins with the in-
duction of anesthesia and position-
ing of the patient for surgery. The
incidence of significant neurologic
injury, including complete paraly-
sis, secondary to spinal or epidural
anesthesia has been reported to be
approximately 0.02%.
5
Injuries re-
lated to these types of anesthesia are

usually secondary to direct mecha-
nisms. These include laceration by
inadvertent needle placement and
compression of the neural elements
secondary to postinjection hema-
toma. Paralysis can occur in patients
with low-lying spinal cords who
undergo routine epidural or intra-
thecal injections of anesthetic agents.
Peripheral nerve injury secondary
to the placement of intravenous
and arterial lines, although uncom-
mon, can also occur.
Peripheral nerve injuries after
lumbar spine surgery more typically
occur secondary to malpositioning
or improper padding of the patient.
In posterior lumbar surgery, the
patient is usually placed in a prone
position on rolls or on a four-poster
padded frame (e.g., Relton frame)
or Andrews-type table. After posi-
tioning, it is important to ensure
that the abdomen hangs free, so as
to minimize intraoperative blood
loss. Regardless of the type of frame
used, well-padded support is neces-
sary, with care taken to avoid exces-
sive pressure on the chest wall and
pelvis. Extra foam padding of the

posts aids in distributing pressure
uniformly to the patient’s skin and
helps to avoid skin blisters and
burns. Every patient should be
positioned and padded as would be
appropriate for a much longer
duration of surgery than projected.
Direct compressive or traction inju-
ries of upper- and lower-extremity
nerves can occur. In particular, ex-
cessive pressure or stretch at the
brachial plexus or femoral nerve can
lead to upper- and lower-extremity
nerve palsies, respectively. In the
upper extremity, the ulnar and an-
terior interosseous nerves are par-
ticularly susceptible to external
pressure, as are the peroneal and
lateral femoral cutaneous nerves of
the lower limbs.
In patients with coexistent cervi-
cal and lumbar stenosis, careful
positioning of the head in neutral or
slight flexion is mandatory to avoid
cervical myelopathy or spinal cord
injury, either while transferring the
patient prone or during final posi-
tioning. A Mayfield three-point
head holder provides very reliable
positioning for long-duration sur-

gical procedures and for high-risk
patients. This avoids pressure on
the face and in particular on the
eyes. Ophthalmic injuries have been
reported secondary to excessive
pressure on the eyes, resulting in
permanent blindness in rare in-
stances.
6
Direct and Indirect
Surgical Injuries
Direct and indirect injuries related to
surgical technique make up the ma-
jority of intraoperative neurologic
complications. Three factors appear
to predispose to iatrogenic injuries:
the relative inexperience of the sur-
geon, failure to follow meticulous
surgical technique, and a history of
prior surgical procedures on the
patient. In patients with undis-
turbed anatomy, the frequency of
injury should be very rare. If inju-
ries are occurring relatively more
frequently, it is mandatory that the
surgeon reevaluate the surgical
techniques employed (Table 1).
Most neurologic injuries from
direct trauma are related to either
trauma by surgical instruments or

placement of pedicle screws or
hooks. Several principles should be
observed to minimize risks. Appro-
priately sized rongeurs down to 1
mm with a small foot-plate should
be available. When removing bone
or soft tissue, one must always
check to see that the dura has been
dissected free (especially in patients
with rheumatoid arthritis) and that
adequate space is available for the
Kerrison foot-plate. If scarring or
adhesions are present, careful dis-
section with angled curettes or
dural elevators is required. If the
area is too narrow, bone must be
removed from above with either
motorized burrs or osteotomes
before rongeurs can be safely used.
Protection of the dura with cot-
tonoid pledgets should be avoided
in these conditions. Use of magnifi-
cation, such as with loupes or an op-
erating microscope, can be helpful
in difficult situations. In general,
Kerrison rongeurs should be directed
parallel to the exiting nerve root to
avoid transection. Motorized burrs
are passed from medial to lateral to
avoid dural damage. Diamond-

tipped burrs with copious saline irri-
gation can be used safely close to the
dura with a lower risk of laceration.
During diskectomy, the exiting
nerve root must be mobilized me-
dially to expose the herniation. In
large herniations, it may not be pos-
sible to completely mobilize the root
without excessive traction. If that is
the case, the disk should be removed
before complete mobilization. Be-
fore incising the disk anulus, one
should always make sure that the
exiting root has been mobilized and
protected. Meticulous hemostasis is
important to avoid mistaking a
nerve root for a disk fragment. The
smallest pituitary rongeurs should
be used to remove the disk, and they
should be opened only after they
have been inserted in the disk space.
Occasionally, the suction tip can
become nicked by another instru-
ment, such as the burr. The sharp
edge created can cause a dural or
nerve root laceration. For this rea-
M. Darryl Antonacci, MD, and Frank J. Eismont, MD
Vol 9, No 2, March/April 2001
139
son, the suction tip should be

checked and discarded if damaged.
Other laceration injuries may
occur with the use of osteotomes
during medial facetectomies and
during aggressive bone removal
with the rongeur. Tearing or rip-
ping of the ligamentum flavum
should be avoided. Particular care
is needed when removing the bone
fragments of the medial facet,
because the capsule of the facet is
often adherent to the ligamentum
flavum or the dura itself. Any
movement of the dura while bone
is being removed, either during
facetectomy or when a Kerrison
rongeur is being used, should alert
the surgeon that such an attach-
ment may be present. Use of a
Penfield or Woodson probe can
help loosen any attachments to the
dura. Performing bone removal
while leaving the ligamentum
flavum intact may also serve as an
added measure of protection to the
thecal sac.
Compression or contusion of the
nerve roots or cauda equina is
another potential type of neurologic
injury related to surgical technique.

Excessive thecal sac retraction,
especially prior to adequate decom-
pression of the spinal canal in pa-
tients with lumbar stenosis, can
cause ischemic injuries. As noted
previously, compression of the the-
cal sac to less than 45% of its cross-
sectional area can cause changes in
motor and sensory root conduction.
Poorly visualized nerve roots are
often subject to such unrecognized
compression. Bertrand described
the “battered-root” syndrome, in
which new-onset numbness after
laminectomy or laminotomy strongly
suggests intraoperative root injury.
5
Excessive compression with cot-
tonoid pledgets, gel foam, or mal-
positioned fat grafts has also been
reported as a source of intraopera-
tive neurologic compromise.
7
The incidence of nerve-root avul-
sion injuries has been reported to
be approximately 0.4%.
5
Forceful
retraction of a nerve root, especially
within a stenotic foramen, can be an

inadvertent cause of a nerve-root
avulsion. This can also occur during
aggressive bone removal. The inci-
dence of conjoined nerve roots in
the lumbar spine has been reported
to be between 2% and 14%,
5
and
probably is more common than is
generally acknowledged. Failure to
recognize a conjoined nerve root
can result in excessive compression,
laceration, or avulsion. Adequately
visualizing the nerve-root sleeve
and working laterally relative to the
nerve root will help to minimize the
incidence of this complication. In
many instances, when the nerve
root cannot be identified or mobi-
lized, it is better to remove more
bone until the pedicle is exposed
than to place undue traction on the
neural elements.
The frequency of dural tears as a
complication of lumbar surgery can
be reduced through meticulous
technique. Although identification
of a dural tear is typically made
after the sudden leak of spinal
fluid, identification of dural tears

that have not yet disrupted the
arachnoid layer is also important.
Most tears can be repaired primarily
with 5-0 or 6-0 suture with a run-
ning stitch. Care must be taken to
avoid incorporating any neural ele-
ments into the closure. After clo-
sure, a Valsalva maneuver aids in
the identification of a persistent or
residual leak. In these cases, rein-
forcement of the repair is possible
Neurologic Complications After Lumbar Spine Surgery
Journal of the American Academy of Orthopaedic Surgeons
140
Table 1
Basic Spine Surgery Technique
1. Ensure adequate exposure and lighting
2. Do not pass instruments over the open wound
3. Avoid overaggressive bone removal
4. Use the Kerrison rongeur with foot-plate oriented parallel to thecal sac
5. Use Kerrison rongeur without upward or downward pressure
6. Leave ligamentum flavum intact to protect thecal sac
7. Do not pull or tear ligamentum flavum
8. Release all tissue attachments to dura
9. Use disposable and undamaged suction tips around thecal sac
10. Be aware of conjoined nerve roots
11. Use knife to incise anulus only vertically
12. Open mouth of pituitary rongeur within disk space
13. Avoid use of electrocautery near the dura
14. Use cottonoid pledgets cautiously

15. Use burr in medial-to-lateral direction under direct visualization
16. Never manipulate thecal sac above L2
17. Never retract thecal sac more than 50%
18. Consider neurologic monitoring
19. Do not leave spikes of bone after decompression
20. Control bleeding with bone wax, hemostatic agents, and cautery
prior to closure
21. Use drains when appropriate
22. Have anesthesiologist do Valsalva maneuver before closure
with muscle or fat grafts sutured
over the repair to the dura. The
use of fibrin glue, which is derived
from equal volumes of thrombin
and cryoprecipitate, may add to the
reinforcement of tenuous repairs.
Larger defects in the dura may re-
quire patch grafting with a seg-
ment of fascia from the paraverte-
bral muscles. Once the repair has
been made, a watertight closure
without wound drains is required
for the overlying fascia, subcuta-
neous tissue, and skin. Postopera-
tively, patients are typically kept
supine for several days to reduce
the hydrostatic pressure on the
dural repair.
Persistent or residual dural leaks
at the time of initial repair may be
treated by the percutaneous place-

ment of a subarachnoid drain im-
mediately after the procedure. The
placement of a subarachnoid drain
above the dural tear allows diver-
sion of spinal fluid and a decrease in
hydrostatic pressure at the repair
site. Patients should be kept supine
after surgery for as long as 5 days,
and prophylactic antibiotic coverage
should be maintained. Continuous
drainage at a rate of 10 to 15 mL/hr
is recommended. In addition, close
monitoring of spinal fluid levels of
protein, glucose, and cell count is
important until the drain is discon-
tinued. Daily Gram stains and cul-
tures of the collected spinal fluid
should also be obtained.
Complications Due to
Changes in Spinal
Alignment
Neurologic complications some-
times occur without an obvious
intraoperative cause. These indirect
injuries are usually the result of dis-
ruption of the vascular perfusion of
the spinal cord or nerve roots. More
commonly associated with scoliosis
surgery, cord ischemia can occur
secondary to application of exces-

sive distraction forces to a relatively
rigid spinal deformity. It can also
occur secondary to excessive hypo-
tension. Any change in neurologic
monitoring signals during these
maneuvers should alert the surgeon
to possible neurologic injury. The
degree of correction of the spinal
deformity should be lessened or
completely released, and a return to
baseline of the evoked potentials
should occur before further reduc-
tion is attempted. In some instances,
the removal of the posterior instru-
mentation is indicated. Ischemic
events involving the spinal cord and
neural elements are estimated to
occur in approximately 1 of every
3,000 surgical procedures for sco-
liosis.
5
Another procedure with high
risk for neural deficit is reduction of
spondylolisthesis. Decompression
of the neural foramina (especially
at L5) before instrumentation and
avoidance of nerve-root compres-
sion from manual downward pres-
sure during the process of drilling,
tapping, and insertion of pedicle

screws or the placement of rods
reduces the risk of neurologic in-
jury. However, root injury is prob-
ably secondary to effective length-
ening of the root associated with
deformity reduction or to release of
reduction or resection of the sacral
dome (sacral shortening).
Injuries Due to
Instrumentation
The risk of neural injury secondary
to aberrant pedicle-screw place-
ment has been reported.
5
A num-
ber of principles should be adhered
to in order to minimize that risk.
The proper starting point should be
identified by using osseous land-
marks or, in cases of severe de-
formity, by directly palpating the
pedicle through a laminotomy.
Once the pedicle has been probed,
it should be checked for inadvertent
perforations. After tapping, the
hole should be checked again for
perforations. Radiography or fluo-
roscopy should be used to evaluate
the placement of screws and the
overall alignment after insertion of

hardware. Intraoperative pedicle-
screw stimulation with electromyog-
raphy is commonly used to ensure
proper pedicle-screw placement.
8
Stimulation of the pedicle screw that
results in nerve-root conductivity
below a certain threshold stimula-
tion can be indicative of screw
breakout or pedicle fracture. Re-
orientation or redrilling of the screw
hole is warranted. Fractures of the
pedicle secondary to screw mis-
placement can also cause direct
nerve-root impingement by the frag-
ment of bone.
Patients noted to have postoper-
ative neurologic deficits or leg pain
after the placement of instrumenta-
tion should be evaluated with com-
puted tomography (CT). This is
preferable to magnetic resonance
(MR) imaging because it accurately
demonstrates screw placement.
Questionable screw placement in
the clinical setting of new-onset leg
pain or neurologic deficit is best
managed by reoperation to remove
or replace the device and to ensure
adequate neural foraminal decom-

pression (Fig. 1).
Posterior interbody grafts, or
cages, used during posterior-lumbar
interbody fusions potentially can
dislodge and impinge on the nerve
roots or cauda equina, causing seri-
ous neurologic sequelae. The inci-
dence of this complication is in the
range of 0.3% to 2.4%.
9
Another
problem with such procedures is
the wide exposure required for graft
insertion, with resultant traction
injury or development of instability.
Anterior interbody devices carry
similar risks with regard to incor-
rect placement and dislodgment.
With the placement of anterior in-
terbody fusion devices, injury to the
hypogastric plexus secondary to the
M. Darryl Antonacci, MD, and Frank J. Eismont, MD
Vol 9, No 2, March/April 2001
141
traumatic exposure can result in
retrograde ejaculation in men. The
incidence of injury to the plexus has
been reported to be in the range of
1% to 5% with the use of these de-
vices, especially when utilizing a

laparoscopic approach.
10
The risk of
such an injury after open anterior
lumbar fusion surgery has been
reported to be 0.42%.
11
Additionally,
malplacement of anterior interbody
devices themselves or expulsion of
disk material posteriorly into the
spinal canal can cause neurologic
compromise, with an incidence of
2% to 4%.
10
Bone Graft–Related
Neurologic Injury
The site from which bone graft is
harvested is often the origin of post-
operative pain. Kurz et al
12
noted a
15% incidence of pain in the first 3
postoperative months. Frymoyer et
al
13
noted this problem in up to 37%
of patients as long as 14 years after
surgery. In many instances, the
postoperative pain was part of a

general pain syndrome. Persistent
pain was more common in patients
in whom the grafts had been taken
from the same side as their preoper-
ative sciatica.
Donor-site pain can also be spe-
cifically related to peripheral nerve
injury. This may be secondary to
involvement of the lateral femoral
cutaneous nerve (meralgia pares-
thetica) during harvesting of ante-
rior iliac crest bone. Nerve symp-
toms may result from entrapment
secondary to scar formation, hema-
toma, or laceration. The variant
anatomy of this nerve as it crosses
the anterior ilium mandates careful
dissection. The incidence of this
complication is reportedly between
1% and 14%.
14
Beginning the inci-
sion at a point 3 cm posterior to the
anterior superior iliac spine lessens
the chance of this complication.
When taking a bone graft from
the posterior iliac crest, one should
be aware of the location of the su-
perior cluneal nerves and the sciatic
nerve.

12
The risks associated with
bone-graft harvesting from this area
can be significant. The incision
should be parallel to the midline, as
the incidence of superior cluneal
nerve injuries increases with exten-
sion of the incision more than 8 cm
lateral to the posterior superior iliac
spine. The superior cluneal nerves
are cutaneous branches of the proxi-
mal three lumbar nerves and sup-
ply sensation to a large portion of
the buttock after piercing the lum-
bodorsal fascia. Although there is a
large degree of cross-innervation,
numbness or painful neuromas
may develop after laceration. Pal-
pation of the sciatic notch may aid
the surgeon in establishing land-
marks for taking the graft and
avoiding injury to the sciatic nerve
or superior gluteal artery. The
direction of use of the osteotome or
gouge should always be cephalad
and tangential to the notch.
Complications in the Early
Postoperative Period
A careful neurologic assessment
when the patient awakens from

surgery provides an index exami-
nation to distinguish a deficit that
may have occurred intraoperatively
from one that occurs in the early
postoperative period. Anatomic
correlation of the neurologic deficit
noted on examination with intraop-
erative events often facilitates early
diagnosis. This is often more valu-
able than attempts at postoperative
imaging with CT, MR imaging, or
plain radiography. Evaluation of
perineal sensation and sphincter
tone is also essential, particularly
after high lumbar surgery when the
possibility of spinal cord injury
exists. The development of neuro-
logic symptoms in a patient who
awakened from lumbar surgery
neurologically intact should alert
the surgeon to the possibility of the
development of new neural ele-
ment compression. The importance
of an early accurate baseline exami-
nation cannot be overemphasized,
as diagnostic imaging of the neural
elements with MR imaging or CT
Neurologic Complications After Lumbar Spine Surgery
Journal of the American Academy of Orthopaedic Surgeons
142

A B
Figure 1 Lateral (A) and anteroposterior (AP) (B) radiographs of a 46-year-old man who
underwent anterior diskectomy with bone grafting and posterior fusion with pedicle
screws 4 years previously. The patient awakened from surgery with severe left leg pain
extending to the dorsum of his foot and was subsequently seen by several physicians.
Radiographs demonstrate misplacement of three of the four pedicle screws.
can be difficult to interpret in the
early postoperative period.
Neurologic deficits that develop
in the early postoperative period (1
to 14 days) usually occur secondary
to retained disk fragments after
diskectomy, postoperative hema-
toma, pseudomeningocele, hernia-
tion of a fat graft, or (rarely) an
epidural abscess. Acute spondy-
lolisthesis secondary to iatrogenic
instability may also present with a
new neurologic deficit. This is more
likely to occur in the late postopera-
tive period; when it does occur in
the early postoperative period, it is
more likely to occur after aggressive
lateral decompressions with viola-
tion of the pars or facet joints. Plain
radiography and CT may be helpful
in the evaluation of this problem.
Recurrent Disk Herniation
After diskectomy for disk hernia-
tion, the incidence of neural com-

pression by a retained or missed
fragment of disk is approximately
0.2%.
15
The patient typically awak-
ens from surgery and reports unre-
lieved symptoms of radiculopathy.
Because early postoperative imag-
ing is difficult to interpret, reexplo-
ration based on the clinical exami-
nation findings and symptoms may
be indicated to ensure the removal
of any remaining disk fragment.
Of course, more than one fragment
may be causing residual compres-
sion. At the time of the index proce-
dure, suspicion that a fragment of
disk may have been missed should
be raised by the presence of friable
disk material or multiple fragments.
Epidural Hematoma
The development of a postoperative
epidural hematoma may be associ-
ated with excessive or poorly con-
trolled intraoperative bleeding. Pa-
tients often have few complaints
initially, but significant increasing
back pain subsequently develops.
This may progress to unremitting
leg pain or even cauda equina syn-

drome in severe cases. Patients with
increasing back or leg pain require
careful monitoring. A complete
neurologic assessment is mandatory,
including a rectal examination and a
check for perianal pin-prick sensa-
tion. If neurologic deterioration oc-
curs, a spinal imaging study, such as
CT-myelography or MR imaging,
should be performed. In obvious
cases, the patient can be immediately
taken to the operating room for
evacuation without imaging. The
presence of an epidural hematoma is
a surgical emergency, requiring
decompression.
Epidural Abscess
In the 2- to 4-week period after sur-
gery, epidural abscess (Fig. 2) be-
comes a potential cause of new-
onset neurologic deficits, although
this is a rare complication. Epidural
abscesses, like hematomas, require
urgent decompression.
Pseudomeningocele
Dural tears that occur during sur-
gery and that are not recognized
and repaired or are inadequately
repaired can result in the formation
of a pseudomeningocele

5
(Fig. 3).
With the increased number of oper-
ations for stenosis being performed,
this complication may be more fre-
quent than previously suspected.
The incidence of pseudomeningo-
cele formation is estimated to be
between 0.07% and 2%.
8
The prev-
alence of incidental durotomy is
higher, at approximately 4%.
8
In-
cidental durotomy is the second
most common cause of lawsuits
after lumbar spine surgery and the
most common complication of re-
peat laminectomy.
8
The formation of pseudomenin-
goceles is more common after lum-
bar spine surgery than after cervi-
cal spine surgery. Although small
dural tears can close spontaneously,
many continue to leak and form
pseudomeningoceles. The use of
agents such as Adcon-L may pre-
cipitate continued leakage of unrec-

ognized dural lacerations.
16
These
can be noted as a slowly expanding
fluid mass or soft-tissue bulging on
physical examination. Patients usu-
ally present with a progressively
worsening headache. Both the
mass and the headache may in-
crease in magnitude on standing.
Diagnosis is readily made early by
using myelography followed by
CT. Magnetic resonance imaging
may also be helpful in the diagno-
sis, but it may be difficult to differ-
M. Darryl Antonacci, MD, and Frank J. Eismont, MD
Vol 9, No 2, March/April 2001
143
Figure 2 T2-weighted MR image of a 50-
year-old man who underwent posterior
laminectomy. Approximately 3 to 4 weeks
after surgery, severe, unremitting back
pain developed. The image demonstrates
enhanced signal in the disk space with
enhancement anterior to the thecal sac
extending cephalad, consistent with an
epidural abscess. Treatment included irri-
gation and debridement and intravenous
antibiotic therapy.
entiate a pseudomeningocele from

a postoperative hematoma with
this modality. The onset of neuro-
logic symptoms may present either
insidiously or acutely with pain,
headache, and sudden neurologic
deficit. A neurologic deficit may
occur when one or more nerve
roots herniate out of the dural tear
and become trapped within the
pseudomeningocele.
Treatment of pseudomeningoceles
includes surgical exploration and
repair. Careful dissection is required.
Excision of the cyst is not necessary,
but opening of the cyst to avoid in-
jury to the trapped roots is usually
required before closure and repair.
Summary
Neurologic complications after
lumbar spine surgery are neither
common nor necessarily foresee-
able. With the increasing number
of lumbar spine operations being
performed, the number of patients
who will sustain neurologic injury
can be expected to increase. Be-
cause of the often irreversible and
dramatic nature of these injuries, as
well as the lack of definitive treat-
ments once they have occurred, it

is obviously best to prevent these in-
juries through use of meticulous op-
erative technique, awareness of risk,
and close attention to perioperative
details.
Neurologic Complications After Lumbar Spine Surgery
Journal of the American Academy of Orthopaedic Surgeons
144
Figure 3 Lateral (A) and axial (B) MR images of a 55-year-old man approximately 4 to 5 weeks after lumbar laminectomy. He reported a
sudden sharp pain with coughing, and a fluctuant mass was noted in his low back. The images demonstrate a large pseudomeningocele.
A B
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