Vol.2, No.7, 395-398 (2013) Case Reports in Clinical Medicine
http://dx.doi.org/10.4236/crcm.2013.27105
Belatedly diagnosed acute motor axonal neuropathy
after cardiac surgery
Chong Tae Kim1,2, Todd Beery2
1Division of Rehabilitation Medicine, The Children’s Hospital of Philadelphia, Philadelphia, USA;
*Corresponding Author: [e-mail]
2Department of Physical Medi cine an d R ehabilitatio n, University of Pennsylvania, Philadelphia, USA
Received 18 March 2013; revised 18 April 2013; accepted 10 May 2013
Copyright © 2013 Chong Tae Kim, Todd Beery. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Surgery has been reported a rare cause of Guil-
lain-Barré syndrome (GBS), but a recent retro-
spective study reported a much higher inci-
dence rate for post-surgical patients. There are
several case reports of GBS presenting after
cardiac surgical procedures. All these cases
were diagnosed as acute inflammatory demye-
linating polyradiculoneuropathy (AIDP). We de-
scribed a case of acute motor axonal neuropa-
thy (AMAN) after cardiac surgery. Clinical fea-
tures were reviewed along with spinal magnetic
resonance imaging (MRI) and cerebral spinal
fluid (CSF) analysis. Sequential electrodiagnos-
tic studies (EDx) were performed. This case
represented a rare complication of AMAN with
urinary retention after cardiac surgery.
Keywords: Guillain-Barré Syndrome; Acute Motor
Axonal Neuropathy; Cardiac Surg ery; Sequential
Electrodiagnosis; Urinary Retention
1. INTRODUCTION
Gullain-Barre syndrome (GBS) most commonly de-
velops following antecedent upper respiratory or gastro-
intestinal infections. Other risk factors for GBS include
vaccination and surgery. GBS is classified into three
types, based on electrodiagnostic findings, which in-
clued acute inflammatory demyelinating polyradiculon-
europathy (AIDP), acute motor axonal neuropathy
(AMAN), and acute motor sensory axonal neuropathy
(AMSAN). AIDP is the most common, and AMSAN is
the rarest. Several cases of post-operative GBS have
been reported [1-6]. To our knowledge, there are no
reported cases of AMAN after an operative procedure.
Herein, we reported a case of AMAN with urinary re-
tention that developed after cardiac surgery. The diagno-
sis of AMAN was confirmed by serial electrodiagnostic
studies (EDx).
2. CASE PRESENTATION
A 24-year-old female with congenital heart disease
(tetralogy of Fallot and absent pulmonic valve) and a
history of prior cardiac heart surgery (main pulmonary
artery banding, ventricular septal defect closure, right
ventricle to pulmonary artery conduit insertion, and right
pulmonary artery placation) as a 2-year-old presented to
a cardiology department of a university children’s hospi-
tal with a gradual decline in general strength and endur-
ance. Prior to developing these symptoms, her physical
function was normal. She was found to have interval
changes of pulmonary stenosis, tricuspid regurgitation,
and aneurismal formation of the left pulmonary artery.
Consequently, she underwent an elective pulmonic valve
replacement, revision of the right ventricle to pulmonary
artery conduit, and left pulmonary artery placation under
general anesthesia. The procedure was completed using
the standard cardiopulmonary bypass and was uneventful.
Preoperatively, she denied having any respiratory or gas-
trointestinal symptoms. Cefazolin was given prior to the
procedure. Total bypass time of the procedure was 89
minutes, and no blood products were transfused. She was
extubated without complications. The medications given
postoperatively consisted of intravenous vasopressors (dis-
continued within 24 hours), furosemide, docu sate, senna,
nalbuphine hydrochloride, and hydromorphone. On post-
operative day 2, she complained of paresthesia and weak-
ness in her bilateral lower extremities. Later that day, she
was unable to stand without assistance and had bilateral
foot drop. On physical exam, manual muscle testing re-
vealed 2/5 muscle strength in ankle dorsiflexors and 4/5
elsewhere in the lower extremities. Both ankle and knee
reflexes were not elicited. Cranial n erves remained intact

C. T. Kim, T. Beery / Case Reports in Clinical Medicine 2 (2013) 395-398
396
and upper extremities were full strength. Sensations to
pain, light touch, proprioception, and vibration were all
preserved symmetrically. An initial magnetic resonance
imaging (MRI) of the thoracolumbar spine performed on
post-operative day 3 indicated no evidence of spina l cord
infarction or abnormal contrast enhancement involving
the cauda equina. Her post-operative course was also
significant for urinary retention, and she was treated for a
urinary tract infection with oral antibiotics (cotrimoxa-
zole 160 mg twice a day) for ten days, however urinary
retention continued to persist. Over the next several days,
lower extremity weakness progressed to 4/5 in hip flex-
ors, 3/5 in knee extensors, and 0/5 in ankle dorsiflexors,
and 2/5 ankle plantar flexors. On post-operative day 5, an
initial EDx was performed and motor nerves (bilateral
peroneal, right tibial, and right ulnar nerves), sensory
nerves (right radial and sural nerves) conduction studies,
and F waves (right tibial and ulnar nerves) were normal,
respectively. A repeat thoracolumbar MRI on post-op-
erative day 6 demonstrated disseminated enhancement of
the peripheral nerve roots of the cauda equina. Lumbar
puncture was performed on post-operative day 7 and
CSF analysis showed elevated protein (86 mg/dL), nor-
mal white cell count, normal glucose (55 mg/dL), nega-
tive oligoclonal bands, and elevated myelin basic protein
(8.10 ng/mL). Compylobacter testing was not performed.
For treatment, a 5-day course of intravenous immu-
noglobulin (400 mg/kg/day) was completed with no cli-
nical improvement. 13 days after her cardiac procedure,
she was admitted to an inpatient rehabilitation unit with
continued bilateral lower extre mity weakn ess and urinary
retention.
During inpatient rehabilitation, she did not make sig-
nificant improvements, and her bilateral lower extremity
weakness and urinary retention persisted. A second EDx
was performed 7 weeks post-operatively showed re-
markably decreased amplitudes of compound muscle
action potentials (CMAP) of the bilateral peroneal nerves.
Right tibial CMAP amplitude was slightly decreased,
and conduction velocities of the bilateral tibial nerves
were minimally slowed. F wave latency of the left tibial
nerve by stimulation at the ankle was within normal
ranges (Table 1). No conduction blocks or temporal dis-
persions were observed. Sensory nerve action potentials
(SNAP) were within normal ranges in the bilateral sural
and left radial, median, and ulnar nerves. Copious fibril-
lation potentials and positive sharp waves with neuro-
genic recruitment patterns were noted in the left lower
extremity (tibialis anterior, gastrocnemius, biceps femo-
ris, and vastus medialis) and less in the lumbar paraspi-
nal muscles. These findings were consistent with AMAN.
At the time of discharge from inpatient rehabilitation, she
continued to have bilateral lower extremity weakness and
paresthesia in a similar pattern as onset. She used loft-
strand crutches to assist with ambulation, and also con-
tinued to suffer from a neurogenic bladder, requiring
intermittent self-catheterization.
3. DISCUSSION
Post-operative acute peripheral neuropathy may de-
velop after any surgical procedure. It can be caused by
various injury mechanisms, which includes mechanical
injury, ischemia, and altered immune system function
that causes an inflammatory neuropathy. The last is be-
lieved to be the p athophysiology of GBS af ter surgery.
Table 1. Electrodiagnostic study.
Side Nerve (M/S)* Distal latency (R/Ref)† (msec) Distal amplitudes (R/Ref) Conduction velocity (R/Ref) (m/s)
Right Tibial (M) 5.9/<6.1 2.7/3 mV 38/>40
Peroneal (M) 5.3/<6.5 0.55/2 mV 46.2/>40
Left Tibial (M) 5.1/<6.1 3.8/3 mV 39.5/>40
Peroneal (S) 5.4/<6.5 0.69/2 mV 42/>40
Ulnar(M) 3.3/<3.5 8/6 mV 58.2/>50
Median(M) 4.4/<4.2 4.3/4 mV 60/>50
Right Sural (S) 4.3/ 35.9 µV
Left Sural (S) 4.3/ 27.7 µV
Ulnar (S) 3.5/ 18.7 µV
Median (S) 3.5/ 31.7 µV
Left Tibial
‡ 49.5/42 - 56
*M/S, motor/sen s ory; †R/Ref, recorded/reference value; ‡, F wave.

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Cases of GBS developing after surgery are reported
with incidence of 5% - 10 %, and are not related to the
type of anesthesia or surgical procedure [1,2]. A recent
retrospective study revealed the relative risk of develop-
ing GBS within the post-operative 6-week period is 13.1
times higher than the general population incidence rate
[2]. All previous cases of GBS after surgery were re-
ported as AIDP with one exception. A case of AMSAN
was reported after a thoracic spine surgery [7]. AMAN is
known to progress faster and reach nadir earlier than
AIDP [8]. This holds true when comparing the onset
times of the cases of post-operative AIDP to the onsets
of our case and the on e case of AMSAN [7] (AIDP post-
operative onset 6 - 40 days versus AMAN and AMSAN
6 - 48 hours). More substantial data is needed to deter-
mine that AMAN or AMSAN develop earlier than AIDP
after surgery.
The pathophysiology of post-operative GBS is not en-
tirely clear. Histologic studies reveal infiltration of ma-
crophages, causing inflammation into the nerve [1]. The
location of the infiltration being in either the axon or
myelin can assist in distinguishing the various subtypes.
Macrophages invade the space between the Schwann cell
and axon not involving myelin in AMAN [9]. Two im-
mune response hypotheses have been proposed to ex-
plain the infiltration process. One of these involves a
T-cell response against antigens on the nerve surface
causing a release of inflammatory mediators [10]. An-
other theory is based on a humoral response from anti-
bodies binding to epitopes on the nerve surface, causing
activation of the complement cascade [11]. There is no
clear understanding on how the two entities are related.
The existing theories regarding the pathophysiology re-
volve around the prin ciple that surgery inherently results
in systemic inflammation [12-14]. The causes of in-
flammation can possibly be induced by ischemia, reper-
fusion injury, and the general trauma of the surgery,
which can consequently cause a humoral and cytokine
response by the immune system. The inflammatory re-
sponse after a cardiopulmonary surgery has been shown
to activate the complement system, causing an increase
of cytotoxic mediators and activation of macrophages,
neutrophils, and T-cells [15]. However, there is no clear
evidence indicating that activating these cells is directly
related to the occurrence of GBS following cardiopul-
monary bypass surgery.
If axonal lesions are limited to the d istal segments, the
recovery is favorable because of good capability of ax-
onal regeneration [16-18]. The poor recovery of our case
can be explained by the lesions involved in proximal
nerve roots as well as distal segments of the peripheral
nerves. As demonstrated in this case, sequential EDx is
necessary to confirm GBS and to classify subtypes, es-
pecially since 10% of cases of GBS have a normal EDx
in the early phase [19,20].
Urinary dysfunction is a common impairment associ-
ated with GBS. The incidence of the impairment is re-
ported in 20% of AIDP cases and 50% of AMAN cases
[21]. Urodynamic studies have demonstrated both detru-
sor overactive and underactive bladders in cases of GBS
[21-23]. Cases of detrusor overactivity in peripheral
nerve lesion is paradoxical, but have been reported in
cauda equina and pelvic plexus lesions [24,25]. Possible
explanations for detrusor overactivity include pelvic
nerve irritation, emphatic transmissions, or an undefined
mechanism [21]. In our case, since the patient deferred
urodynamic study, it is unclear whether the bladder was
overactive or underactive. Since the patient had sustained
urinary retention, it is assumed to be an underactive
bladder.
4. CONCLUSION
To our knowledge, five cases of AIDP were reported
after cardiac operative procedures. This is the first report
of AMAN after a cardiac operative procedure, and re-
quired sequential EDx for diagnosis.
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