Keywords
Anaesthesia - atlanto-axial dislocation - Morquio A syndrome - mucopolysaccharidosis
INTRODUCTION
Mucopolysaccharidosis (MPS) refer to an inherited group of diseases caused by deficiency
of different lysosomal enzymes responsible for degradation of glycosaminoglycans.
Intracellular accumulation of these partially metabolized glycosaminoglycans hinder
normal functioning of the tissues involved. Morquio A syndrome (MPS IV-A) is an autosomal
recessive MPS caused by deficiency of N-acetyl galactosamine-6-sulfatase enzyme resulting
in deposition of large amount of keratan sulphate and chondroitan sulphate in various
tissues of body.[1] The manifestations are primarily due to mesenchymal abnormalities and mental intelligence
is normal.
Nearly every system of body may be involved affecting anaesthetic preparation and
management. Cervico-vertebral junction anomaly, deposition of mucopolysaccharides
in various airway structures and involvement of temporo-mandibular joints result in
a difficult airway state.
We hereby report a case of MPS IV-A with atlanto-axial dislocation (AAD) scheduled
for transoral odontoidectomy and posterior fixation.
CASE REPORT
A 6-year-old female child known case of MPS IV-A, weighing 14 kg was admitted with
history of gradually increasing weakness of all limbs for last 5 years and increased
frequency of micturition for last 7 months. Patient had a complete cessation of growth
for last 2 years and at present, height was 120 cm. She had normal developmental milestones
and intellect with no history of obstructive sleep apnoea.
On examination, the child had a short stature with dolichocephaly, short neck, kyphosis
at thoraco-lumbar region, pectum excavatum with prominent costal margins, genu valgum
and equino valgum [Figure 1]. Central nervous system examination revealed a power of 4/5 in all limbs with spasticity
and brisk reflexes. Computed tomography (CT) scan of craniovertebral junction showed
AAD with obliteration of normal cervical lordosis with occipitalisation of C1 posterior
arch. Patient was planned for occipitocervical fusion with sublaminar wiring.
Figure 1: Image of the patient showing pectum excavatum with prominent costal margins and short
neck
Preanaesthesia assessment revealed a systolic murmur at apical area on auscultation
which was confirmed by echocardiographic finding of myxomatous degeneration of heart
valves with moderate mitral regurgitation with normal left ventricular function. Airway
examination revealed adequate mouth opening with Mallampati grade II with large tongue
and short neck. A cervical collar was placed around neck. X-ray neck revealed enlarged
soft tissue shadow in prevertebral area with apparently normal laryngeal and tracheal
contour [Figure 2]. Possibility of difficulty in securing airway was anticipated in view of presence
of congenital AAD, large tongue, short neck, soft tissue deposit and cervical collar
in situ. Preoperative complete haemogram, renal function test, lung fields on chest
X-ray were normal. Bedside pulmonary function tests (PFT) of the patient were equivocal
as the child could not cooperate to maximum ability. We did not administer infective
endocarditis (IE) prophylaxis, as there is no recommendation regarding IE prophylaxis
in a patient with congenital mitral regurgitation, according to the guidelines.[2]
Figure 2: X-ray neck showing soft tissue mass in prevertebral area with normal laryngeal and
tracheal contour
Patient was premedicated with intravenous glycopyrrolate 0.1 mg, 10 min before induction
of anaesthesia. Difficult airway cart was prepared in view of anticipated difficult
intubation. It comprised oral airways, stylets and bougie, laryngoscopes with Miller
and Macintosh blades, different sizes of endotracheal tubes, laryngeal mask airway
(LMA), paediatric fibreoptic bronchoscope, glidescope, equipment for cricothyrotomy
and surgical tracheostomy. The neurosurgeon was present in the operating room and
was asked to be prepared for performing tracheostomy, in case need arises. Anaesthesia
was induced with sevoflurane following which a peripheral venous access was secured.
Intravenous (iv) fentanyl 2 μg/kg was administered and after ensuring adequate mask
ventilation, rocuronium 10 mg iv was given. Patient was intubated successfully with
5.5 mm cuffed, oral, flexometallic tracheal tube with the help of paediatric fibreoptic
bronchoscope. Maintenance of anaesthesia was done with sevoflurane in air/oxygen mixture
and intermittent boluses of rocuronium.
Monitoring included electrocardiography, pulse oximetry, invasive arterial blood pressure,
urinary output and endtidal CO2 and anaesthetic gas measurement. Heart rate was kept
between 90 and 100/min to decrease the regurgitant flow across mitral valve. Patient
was carefully positioned prone for surgery. Surgery lasted for an uneventful period
of 4 hours.
At end of posterior fixation, patient was turned supine anda check larngoscopy was
performed to assess the laryngeal view. A complete glottic view was visualized [Figure 3] and subsequently, neuromuscular blockade was reversed.[15] When child became fully conscious with resumption of normal breathing, trachea was
extubated without any complication. She was then transferred to the neuro-intensive
care unit (NICU), where she recovered uneventfully and was monitored overnight. Duration
of intensive care unit (ICU) stay and hospital stay was 1 and 5 days, respectively.
At the time of discharge, spasticity had decreased with power 4/5 power in all limbs
and glasgow outcome scale (GOS) was 4.
Figure 3: Glidescopic view clearly showing full view of glottis
DISCUSSION
The multisystemic involvement[3]
[4]
[5]
[6]
[7] in a patient with MPS IV-A makes thorough preoperative assessment imperative. Based
on the findings [Table 1], adequate preparation should be done to avoid any sudden crisis.
Table 1
Multisystemic involvement in Morquio A syndrome
|
System
|
|
Cardiac
|
|
Valvular regurgitant or stenotic lesions, reduced myocardial compliance, hypertension,
coronary disease, arrhythmias, cardiac failure
|
|
Respiratory
|
|
Macroglossia, dental abnormalities, short neck, subglottic narrowing, hanging epiglottis,
oro-pharyngeal deposits, large adenoids/tonsils, restricted opening of temporomandibular
joints, restrictive and even obstructive respiratory pattern
|
|
Vertebral
|
|
Cranio-vertebral junction anomaly, odontoid hypoplasia, cervical cord compression
|
|
Skeletal
|
|
Short stature, short diaphysis, curved metaphysis, poorly developed epiphysis, wide
acetabula, hypoplastic femoral heads, pigeon chest, genu valgum, equino valgum
|
|
Others
|
|
Prognathism, hepatomegaly, corneal clouding, glaucoma, degenerative retinal lesions,
hearing loss
|
Several authors have highlighted airway abnormalities in these patients. Not only
it is difficult to intubate trachea but also structural changes may lead to laryngeal
stenosis and distorted lower airway resulting in ventilation problems. History of
obstructive sleep apnoea (OSA) has been found to be associated with difficult airway.[8] Such children are prone to respiratory obstruction during induction of anaesthesia
and post extubation. The incidence of difficult intubation in patients with Morquio
syndrome varies from 0–50%.[9]
[10]
[11] In a retrospective review of 17 patients of MPS, overall incidence of difficult
intubation was 25%; highest in MPS VI (86.7%) and 0% in MPS IV.[9] However, small number of MPS IV patients in study population may be responsible
for this finding.
The decision regarding airway management can be based on radiology findings. In our
patient, the preoperative X-ray neck did not show any evidence of laryngeal or tracheal
stenosis. Another modality like preoperative multidetector computed tomography film
can also delineate airway anatomy and assist in decision-making regarding intubation
and extubation.[12] Recently, use of ultrasound for assessment of airway anatomy has also been highlighted.[12] This simple method not only allays the harmful effects of radiation but can also
give a real time picture.[13]
Rigid instruments like glidescope, lighted stylet etc., are preferred for intubation
in these patients as they can displace soft tissue more easily than flexible fibrescope.[10] We opted for flexible bronchoscope as the first choice as it causes no movement
at atlanto-axial joint. Several authors recommend awake fibreoptic intubation and
avoiding muscle relaxants for this purpose. As our patient was a child, we did not
resort to awake intubation. Though the intellect is normal in these patients, behavioural
abnormalities like anxiety and depression are known to occur.[14] We were successful in intubating the patient with fibreoptic bronchoscope under
anaesthesia in the first attempt. Literature search reveal reports of augmented difficult
intubation once the patient is paralysed. Loss of muscular tone and floppy soft tissues
after administration of muscle relaxants, makes fibreoptic intubation after induction
of anaesthesia even more difficult.[7]
[15] Supraglottic airway device such as I-gel has also been used successfully used as
a channel for fibreoptic-guided tracheal intubation in a patient with Hunter syndrome.[16] The ability to mask ventilate and back-up of glidescope, cricothyrotomy and tracheostomy
made us go ahead with muscle relaxation. The choice of muscle relaxant is debatable
and many will straightway negate the use of rocuronium in such cases and will prefer
to use succinylcholine if at all. But we want to emphasize that succinylcholine is
contraindicated in such cases of upper motor neuron paresis and should not be used.
Life-threatening hyperkalaemia may complicate the anaesthetic management and even
cardiac arrest may ensue. However, another safer alternative could have been fibreoptic
intubation under sevoflurane induction along with ‘spray as you go technique’ omitting
the administration of muscle relaxant. The inhalational induction also allows rapid
awakening in case intubation fails. Fibreoptic intubation under dexmedetomidine sedation
with preservation of spontaneous breathing is another alternative. Fibreoptic intubation
under influence of muscle relaxants requires expertise and should only be attempted
if one is proficient and has back-up help. In a difficult airway situation, we should
use the technique we are comfortable with.
Posterior fixation renders the airway more difficult. So at the end of surgery, we
did a check laryngoscopy with glidescope to assess the laryngeal view [Figure 3]. An indirect glottis visualization with help of videolaryngoscope can help in assessing
the airway at time of extubation in cases where posterior fixation of cervical spine
has been done. If reintubation is required in cases where extension of cervical spine
is absent, at least we can be sure of being able to visualize glottis with videolaryngoscopes.
With additional help of stylet/bougie, we expect to be able to reintubate 100% of
patients.
Absence of OSA, uneventful intubation at start and visibility of full glottis on check
video laryngoscopygave an assurance that we can go ahead with extubation of trachea.
Patients may require continuous positive airway pressure in the postoperative period
and should be closely watched for any desaturation episodes.
CONCLUSION
MPS IV-A affects multiple systems and patient should be assessed in total. Then, depending
on the expertise and resource availability, an individual anaesthetic plan can be
chalked out for these patients. Decision to extubate the patient can be reinforced
by a check laryngoscopy with help of video laryngoscope.
