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Anesthetic management
Regional anesthesia is not contraindicated in patients with fixed
Syringomyelia is a neurological disorder characterized by the for-
neurological deficits, or previous spinal surgery. Although it may
mation of cystic cavities within the spinal cord, typically in the
be more technically difficult, a high success rate for labor epidural
cervicothoracic regions. Syringomyelia most often is congenital,
analgesia in patients with spinal instrumentation can be achieved
associated with Chiari I malformations (see Figure 10.5).193 The
with prudent persistence.73,190 There is concern about potential
pathogenesis is unclear. However, 84% of patients have cranio-
increased rates of accidental dural puncture and incomplete
blocks.179,189 Some recommend performing the epidural above cervical junction abnormalities, which may be the initiating cause
of the cystic lesions because of the development of a craniospinal
the lesion level, if possible, to decrease the likelihood of an abnor-
mal epidural space and hence dural puncture.189 Use of the pressure gradient. Other causes of syringomyelia include trauma,
arachnoiditis, and spinal cord tumors.194,195,196,197 Traumatic syr-
hanging drop or air balloon technique to identify the epidural
inxes following obstetric epidural and spinal anesthesia have been
space may be more effective if abnormal ligaments are present,
described with all of the patients suffering neurological symptoms
although relatively few anesthesiologists have experience with
from the cystic lesion.198,199
these techniques.189 The local anesthetic dose requirements in

Chapter 10

labor pose a theoretical risk of brain-stem herniation and cord
compression,202,203 although neither of these complications has
been reported. There is a paucity of literature on the obstetric and
anesthetic management of women with syringomyelia. The
largest series by Mueller involved seven women, from which it
appears that pregnancy does not affect the symptoms of the
disease and vice versa.203 A review of Chiari I malformations,
with or without syringomyelia, in 12 parturients revealed no unto-
ward effects from vaginal delivery.204 The decision about mode of
delivery should be made in consultation with a neurosurgeon, and
will depend upon maternal symptoms during pregnancy.202,203

Anesthetic considerations for labor and delivery
The most important pathophysiologic features are neurologic
dysfunction and respiratory impairment secondary to kyphosco-
liosis. Even in parturients without hydrocephalus, one must be
concerned about the effects of sudden increases in ICP on the
cystic cavities typical in syringomyelia. Sudden clinical deterio-
ration in patients with syringomyelia following a short period
of Valsalva maneuver has been documented in the past.205
Involvement of the autonomic system in patients with syringo-
myelia is common, especially if syringobulbia is present, resulting
in altered cardiovascular responses to vasodilation and hypovo-
lemia. Slow induction of regional anesthesia/analgesia is
The flow dynamics of CSF are very abnormal in syringomyelia,
therefore spinal anesthesia is unpredictable, and continuous
spinal anesthesia would be a better choice. Some authors con-
sider a Chiari malformation and/or syringomyelia an absolute
contraindication to regional anesthesia, some only to spinal
anesthesia.194,196,206,207,208,209 There is one case report of a Chiari
Figure 10.5 T2-weighted sagittal MRI of the upper spinal cord showing a syrinx
I malformation diagnosed two weeks postpartum in a woman
typical of syringomyelia. Reproduced with permission from: Murayama K.
who developed nystagmus following a large-gauge-needle dural
Cesarean section in a patient with syringomyelia. Can. J. Anesth. 2001; 48: 474“7.
Fear of large-gauge dural puncture with an epidural needle and
the subsequent alterations in CSF pressure leading to brain her-
Syringomyelia is classified as communicating (with CSF path-
niation are theoretical, but possible. However, epidural anesthe-
ways) or noncommunicating. Communicating syringomyelia is
sia has been used successfully for labor analgesia and C/S in
considered more susceptible to deterioration when exposed to
raised ICP.200 Extension of the syrinx cephalad into the medulla is several cases of syringomyelia with or without a Chiari malforma-
tion.202,203,205 Nel et al. reported on the uneventful use of epidural
known as syringobulbia.
anesthesia for C/S in a woman diagnosed with a Chiari I malfor-
Typical symptoms of syringomyelia are progressive sensorimo-
mation three months prior to becoming pregnant.205 She refused
tor deficits of the upper limbs, and often neuropathic pain. Pain
decompression surgery, had worsening headaches during preg-
and temperature are commonly affected, while touch and posi-
nancy and so had an elective C/S.
tion sense are usually preserved. Diagnosis is made based upon
The presence of a shunt for hydrocephalus, or syringomyelia
clinical features, supported by MRI, and often is not made until
alone, is not a contraindication to regional anesthesia. However,
patients are in their third or fourth decade. Secondary kyphosco-
13“23% of parturients may experience shunt problems during
liosis due to weakness of the paraspinal muscles is common;
pregnancy, some requiring revision, others waiting until
however, the development of this structural abnormality may be
postpartum.182,211 Neurosurgical consultation is recommended.
reduced by early suboccipital craniectomy.193 Arai et al. showed
Prophylactic antibiotics are often recommended, as is a shor-
that syringomyelia and Chiari malformation may be diagnosed
during investigation of progressive scoliosis in children.201 There tened second stage. One should enquire about clinical features
of raised ICP prior to using neuraxial anesthesia.
have been cases of terminal syringomyelia associated with occult
Considerations for GA include avoidance of succinylcholine,
spinal dysraphism. Obviously these cases will have lower limb,
sensitivity to nondepolarizing neuromuscular agents,207 involve-
rather than upper limb, neurological deficits.164,195
ment of bulbar nerves affecting airway reflexes, effects of respira-
Syringomyelia is a progressive myelopathy in two-thirds of
tory compromise on postoperative course, and control of ICP.
affected patients. The physiologic changes of pregnancy and

3 Nervous system disorders

Interestingly, some authors feel that GA should be avoided in neurological improvement following surgery is much more
impressive in Group 2 patients.167
these patients secondary to concerns about sudden increases in
ICP during induction and emergence.202 Roelofse et al. reported In adults, the major complaint is pain230 (80% in study by Pang
and Wilberger222), usually in the lower limbs and perineal region.
on C/S under GA (they considered regional absolutely contra-
indicated) in a parturient with syringomyelia, who awoke with In most adults the lower back and leg pain is worsened upon
new sensory disturbances that resolved within 24 hours.208 There performing the ˜˜three B signs™™ described by Yamada et al.: (1)
were no specific measures to control ICP during the anesthetic. sitting in the ˜˜Buddha™™ postion, (2) difficulty Bending slightly at
the waist while performing tasks such as dishwashing, and (3)
holding light material like a Baby at waist level while standing.167
Tethered cord syndrome
Other presenting symptoms include sphincter dysfunction (57%),
Tethered cord syndrome (TCS), also known as ˜˜tight filum termi- leg weakness and sensory deficits (65%), as well as trophic ulcera-
tions.219,220,221,222,227 Cutaneous stigmata of spinal dysraphism
nale,™™ ˜˜cord traction syndrome,™™ ˜˜filum terminale syndrome,™™
and ˜˜tethered conus,™™ was first described in 1953 by Garceau, such as dorsal midline nevi, lipomas, skin tags, dimples, and
although it was probably reported as early as 1918.212,213 It is a hairy patches are found in only 50% of adult TCS but are very
common in childhood TCS.216,217,238 Similarly, foot deformities
neurological syndrome caused by longitudinal traction on the
conus medullaris. Initially recognized in pediatric postmeningo- and progressive scoliosis are unusual in adults and more
myelocele repair patients, it is an accepted, albeit rare, entity in common in children. Often a precipitating event, such as child-
adults. There are over 200 case reports of patients presenting birth (lithotomy position), sexual intercourse, motor vehicle acci-
dents causing hip flexion, exercising and weight lifting,220,232
between the ages of 17 and 76 with a mean age of symptom
onset of 30“33 years and a mean age of diagnosis of 37“39 lumbar spondylosis and herniated discs, direct blows to the
years.214,215,216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233 back, and falls on the buttocks,222 initiates the symptoms of
Tethered cord syndrome is commonly associated with spinal dys- adult-onset TCS.
raphism, with varying degrees of incomplete fusion of the neural The most useful diagnostic tools are CT scan and MRI, with MRI
now the imaging method of choice (see Figure 10.6).219,220,221,224,230
arch. Other anomalies include spina bifida occulta (the most fre-
quent finding in adults),215,221 diastematomyelia, syringomyelia, Myelography will demonstrate the position of the conus medullaris
lipomas, dermoid cysts, intra- and extradural bands, and menin- as well as the classical horizontal or cephalad direction of exiting
gocele manque.216,217,231,234 sacral nerve roots. It does not delineate well the underlying cause.
The underlying pathology causing cord tethering includes Plain radiographs of the spine reveal vertebral anomalies in more
thickened filum terminale (33“69% of cases),235 intradural than 95% of adults.217,222,223 Use of CT scans, MRI or direct exam-
lipoma, spinal adhesions, and postsurgical fibrous bands. A thick- ination at surgery reveals that 70% of adult patients have elements
of spinal dysraphism, other than spina bifida occulta.217 Initial
ened filum terminale is the most common finding in adults,
although there is often more than one pathological finding. descriptions of the syndrome required that the conus be in an
Almost all children who have had a meningocele repair have
evidence of a thickened filum and/or low placed conus medul-
laris, yet only 15% develop TCS.212,236,237 The onset of symptoms
is related to the degree of traction on the conus. Symptoms in
adults occur in two patterns: there is direct trauma to the spine or
momentary excessive stretching of the tight conus by extreme
flexion of the neck or hips; or a pattern of longstanding mild and
static neurological symptoms that suddenly progress or wor-
sen.167,222,231 In the largest published series on adult-onset TCS,
44% followed the second pattern.222 Some postmeningocele
repair patients do not present with TCS until adolescence, and
do not fit either of the above patterns.212,226,237
Recognizing that many patients with TCS reach adult age prior
to becoming symptomatic from spinal cord dysraphism, Yamada
recommended a new classification of TCS.167 Group 1 (10/70
patients in Yamada™s 2000 series) are those with known spinal
dysraphism since birth but stable neurologically until adulthood.
Group 2 (60/70 patients) are those who were asymptomatic dur-
ing childhood, developing neurological symptoms after their
teenage years, with no evidence of other spinal dysraphic fea-
tures. The majority of these Group 2 patients are in fact ˜˜failed
back syndrome™™ patients, in whom a tethered cord was not Figure 10.6 MRI scan of 23-year-old female with a tethered spinal cord.
recognized as the cause of chronic back pain with neurological White arrow indicates conus medullaris, located at the level of the L3 vertebral
symptoms. Both groups manifest similar symptoms; however, body.

Chapter 10

There are two case reports of young, female patients presenting
with classic lumbar disc symptoms of radicular pain and derma-
T12 “ L1
1 tomal sensory loss.224 One had spina bifida occulta at L3“4, the
L1 5 other had normal plain x-rays. Both had a low-lying conus at L4
L1 “ L2
and neither had cutaneous stigmata. Another case report
L2 involved a woman with a history of persistent back pain and
L2 “ L3
bladder symptoms following a previous pregnancy.225 She had
L3 no cutaneous stigmata, spina bifida occulta at S2, and low-lying
L3 “ L4
conus. The underlying pathology of her TCS was a choriostoma.
L4 Another case report described a woman with a history of giant
L4 “ L5 lumbar hairy nevus who developed new unilateral neurological
symptoms following delivery with epidural analgesia.240 On MRI
L5 11
she had a tethered cord and, on clinical examination after deliv-
L5 “ S1 12
ery, a smaller right foot and absent ankle jerk. The precipitating
2 factor of the new neurological symptoms could have been fetal
S1 “ S2
head compression, position during childbirth, or the epidural
S2 “ S3
itself. Another parturient with known congential lumbosacral
lipomyelocele had an MRI during pregnancy that revealed a teth-
ered cord at L4, the same level as the intraspinal lipoma. An
epidural was placed at L2“3 for labor analgesia, knowing that
Figure 10.7 Graph shows distribution of the positions of the coni in 229 patients
caudal spread might be impaired. The epidural was successfully
with tethered cord syndrome. Data from references 232,247,254.
topped up for surgical anesthesia 18 hours later. There were no
new neurological symptoms postpartum.241
abnormally low position, defined as below the body of L2.213,222
Anesthetic management in parturients with
However, in adults 15“35% of patients with TCS will have a nor-
mally positioned conus (see Figure 10.7).167,217,223 One study classi- tethered cord syndrome
Clinically, the importance of this syndrome lies in the greater
fied patients with TCS as Group 1 and 2 and found that the conus is
below L2“3 in all Group 1 patients, but only 65% of Group 2.167 potential for direct spinal cord trauma while performing regional
anesthesia, due to the low-lying and posteriorly displaced conus
Magnetic resonance imaging shows that in almost all adults with
medullaris. This is especially important given the recent evidence
TCS, the conus is posteriorly displaced within the spinal canal and
attached to the posterior arachnoid membrane.239 This conus posi- that anesthesiologists tend to be at least one level higher than
they think when performing regional anesthesia.242 Also, the syn-
tion means extreme care must be taken during epidural or spinal
drome may not become symptomatic until there is a precipitating
anesthesia, as direct needle trauma is more likely than if the conus
event such as childbirth, following which regional anesthesia may
was merely low lying.
be implicated. The risks of epidural anesthesia in this group of
Surgical release of the filum terminale relieves tension and
patients are unknown.
results in dramatic improvement in pain symptoms and motor
As TCS may not be diagnosed until adulthood it is important to
and sensory function. Unfortunately, sphincter function often
remains impaired.216,222 Despite this, neurosurgeons now take a careful history and perform a neurological examination in
all parturients requesting regional anesthesia who complain of
recommend surgical intervention in adults diagnosed with
TCS. 167,214,232,233,235 significant back pain or neurological symptoms. In patients with
known TCS, regional anesthesia is not contraindicated but should
Although rare, adult-onset TCS does occur during the child-
bearing years.219,221,222,225,232 In Huttman et al.™s series of 54 cases be performed below the level of the conus if known, or as low as
possible if not. Informed consent in these patients should include
of TCS, 11 presented as adults, and of those 5 experienced first
symptoms during pregnancy and/or delivery.232 The presenting a discussion on the increased risk of spinal cord trauma. Direct
needle trauma to the conus does not necessarily produce typical
symptoms of back pain and urological problems may delay diag-
lancinating pain,199,236 but such pain on performing a regional
nosis of the syndrome or result in misdiagnosis.219,233 The under-
technique mandates immediate removal of the needle or cathe-
lying pathology frequently discloses the presence of spina bifida
ter. Epidural anesthesia may be safer than spinal anesthesia
occulta, and in 85% of cases the conus medullaris ends below the
because of the low fixed spinal cord. Intrapartum management
body of L2. Evidence for adult-onset TCS includes the presence of
of patients with known TCS should include avoidance of pro-
static neurological deficits from childhood; pain in the perineal,
longed lithotomy position and squatting.
anal, and gluteal regions, or the lower limbs, which may worsen
with prolonged bed rest; shock-like sensations up and down the
spine on forward bending similar to Lhermitte™s sign; bilateral
Anterior spinal artery syndrome
lumbosacral sensorimotor deficits; cutaneous stigmata; and
Anterior spinal artery syndrome (ASAS) is a rare neurological
bladder complaints with spastic symptoms predominating over
syndrome caused by occlusion of the anterior spinal artery,
hypotonic symptoms.

3 Nervous system disorders

usually in the lower thoracolumbar cord area.243,244 First reported process is limited to high-dose steroids for vasculitis,247 or anti-
coagulants and antiplatelet agents for embolic phenomena.248 In
in 1909, ASAS describes a constellation of neurological symptoms
(dissociated sensory function with preservation of proprioception one report, three patients in the acute phase were given injections
and light touch, and loss of motor function) caused by occlusion of of dexamethasone and urokinase directly into the artery of
Adamciewicz with good results.246 Recovery from the syndrome
the anterior spinal artery. Often the onset of neurological symp-
toms is preceeded by sharp back pain.245 Pathophysiological is limited in those patients with occlusive lesions, aortic disorders,
events leading to ASAS include vessel occlusion, marked vasocon- and angiomas. Residual bladder dysfunction often remains, even
when there is improvement in motor and sensory function.246
striction, or local interference with spinal cord blood flow. It is
usually seen in the older atherosclerotic population associated There are case reports of anterior spinal artery thrombosis in
younger patients with a vascular malformation of the cord.249
with aortic reconstructive surgery, or associated with significant
hypotension in the presence of major regional anesthesia. It may There is one report of a diabetic patient with scleroderma who
occur in younger patients with underlying vasculitic diseases (see
Table 10.6).
Table 10.6 Reported causes of anterior spinal artery
Spinal cord blood supply is derived from the anterior and
syndrome a
posterior spinal arteries. A single anterior spinal artery supplies
Most frequent (greater than 20 cases)
the anterior two-thirds of the spinal cord, areas which subserve
Thoracic aneurysm repair
motor and coarse sensory function (see Figure 10.8). It originates
Abdominal aneurysm repair
at the foramen magnum from branches of the vertebral arteries
Less frequent (10 to 15 cases)
and, during its course down the spinal cord, receives contribu-
Epidural epinephrine use
tions from seven to ten radicular arteries. It does not have a well
developed continuous course, and the feeder arteries from the
descending aorta are variable.107 The major supply in the lower Spinal cord angioma
Rare (less than 10 cases)
thoracic and lumbar cord is from the artery of Adamciewicz,
which enters the cord between T5 and L4. If the artery enters
high there are few thoracic medullary vessels, and less vascular
Metastatic cancer
supply to the thoracic cord. The paucity of supply and poor
Cervical spondylosis
anastomoses between the anterior and posterior spinal arteries
Mitral valve emboli
create watershed areas in the cord where supply to the spinal cord
is tenuous, most notably the lower thoracic spinal cord.
Anterior spinal artery syndrome is diagnosed on the basis of a
Vigorous exercise
combination of clinical findings and radiographic evaluation.
Spontaneous epidural bleed
Clinically, there is usually sudden onset of progressive parapar-
Intravenous vasoconstrictor use
esis, bladder dysfunction, and sensory loss to pain and tempera-
ture. Some patients experience pain in the neck or back prior to a
Excluding 17 cases of unknown etiology.
onset of neurological symptoms.246 Magnetic resonance imaging
Data from references: 96,106,243,244,245,246,247,248,249,250,251
has replaced myelography and angiography of the spinal cord as
the diagnostic technique of choice.243 Treatment to reverse the

Figure 10.8 Cross-section of the spinal cord showing arterial
blood supply and areas of sensorimotor function.

Chapter 10

developed ASAS following epidural anesthesia for C/S.250 There 86 mmHg) with a bilateral T10 block. After stabilization with a
was no hypotension during anesthesia, and the patient was noted fluid bolus, she was given 5 ml of 3% chloroprocaine for the C/S.
to be paraparetic 12 hours after the effect of the epidural abated. She developed classic ASAS diagnosed six hours postoperatively,
An epidural hematoma was ruled out, but the epidural venogram the MRI at 48 hours showing an ischemic spinal cord from T4 to
L1.258 There were no underlying abnormalities of the spinal cord.
revealed a compressed, collagen-filled epidural space with poor
venous supply. It was postulated that local anesthetic injection The authors postulated the combination of brief hypotension and
produced a sudden marked rise in epidural pressure, which an epinephrine-containing epidural infusion was the cause of the
caused compression of the vascular supply. There are three case ASAS. Many parturients experience the same conditions without
reports implicating epidural catheter irritation as a cause of developing ASAS, however.
vasospasm of the anterior spinal artery or segmental feeder In the childbearing population, arteriosclerosis is uncommon
arteries. Two involved an epidural for labor analgesia.245,251 In but diseases with vasculitic components such as SLE, sclero-
one case, a woman for elective C/S had an L3“4 epidural derma, and Takayasu arteritis may be present and can affect
placed.245 During advancement of the catheter she complained spinal cord blood flow.247 In these patients it is prudent to avoid
of paresthesias in her arms and legs. The catheter was used, but the use of epinephrine or other vasoconstrictors in the epidural or
with each top-up the patient complained of similar pain. General subarachnoid spaces. Vigilance in the detection and correction of
anesthesia was administered, but on emergence the patient had hypotension in the parturient reduces the occurrence and dura-
persistent paralysis, diagnosed ultimately as ASAS.245 The second tion of severe hypotension during major regional blockade, a
condition linked to the development of ASAS.106,256 The differen-
patient developed sudden onset of paraparesis with preservation
of posterior column function shortly after delivery.251 The epi- tial diagnosis of neurological impariment following epidural
dural catheter was removed and there was complete resolution of anesthesia includes direct needle trauma, chemical myelopa-
the neurological symptoms over 30 minutes. In the final case, thies, symptomatic decompensation of coincidental tumors or
postoperative analgesia provided by an epidural caused a similar vascular malformations, and infection.
transient ASAS.252
Anesthetic considerations in anterior

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