Delayed emergence following surgery associated with inadequate respiratory effort and muscle weakness is usually attributed to the residual effects of anaesthesia. However, if the clinical features persist for longer than anticipated, then a more serious aetiology should be suspected. Acute neurological deterioration may be caused by an iatrogenic event, as a complication of an underlying disease or due to a co-existing, but previously undiagnosed, pathological process.
Neurological deterioration in a child following routine surgery, although rare, has potentially life threatening consequences. We report the case of a child who, following adentonsillectomy, developed quadriplegia and acute respiratory distress due to previously undetected atlanto-axial instability. Patients with atlanto-axial instability often have mild or non-specific symptoms, despite severe cervical cord compression. Subtle manifestations may be ignored or attributed to other disease processes, which render patients with undiagnosed atlanto-axial instability at risk of serious neurological injury during general anaesthesia, particularly at the time of laryngoscopy and tracheal intubation.
A 7-year-old, 25-kg male patient was scheduled for an elective adenotonsillectomy for sleep-disordered breathing and recurrent tonsillitis. Anaesthesia was induced with intravenous fentanyl 50 μg, and thiopental 125 mg. After atracurium 15 mg, direct laryngoscopy revealed a Cormack and Lehane grade-1 view of the glottis and tracheal intubation was performed uneventfully using a 5.5-mm for cuffed tracheal tube. Anaesthesia was maintained with isoflurane at an end-tidal concentration of 1.0–1.5% in 60% nitrous oxide in oxygen. Surgery was performed with the patient in the Rose position (head extension with a roll placed underneath the shoulders) and lasted 40 min, during which a further atracurium 5 mg was given. Postoperatively, the patient was drowsy and demonstrated no spontaneous respiratory efforts for 50 min after the end of surgery, following which reversal of neuromuscular blockade was attempted with intravenous administration of neostigmine 1.0 mg and glycopyrronium 0.2 mg. There was inadequate recovery of respiratory and neuromuscular function, and the patient was agitated, in respiratory distress and was noted to have weakness of all four limbs. He was tachypnoeic, with a respiratory rate of 40 breaths.min−1, the end-tidal carbon dioxide level was 7.2 kPa and the arterial oxygen saturation was 89% breathing 50% oxygen. The patient was haemodynamically stable, normothermic and had clear lung fields on auscultation. No obvious cause could be determined and an additional dose of neostigmine 0.25 mg and glycopyrronium 0.05 mg was administered. There was no improvement in the respiratory insufficiency or quadriparesis over the next 2 h. The possibility of an acute neurological event was considered and the decision was made to transfer the patient to our institution. His trachea remained intubated and the lungs ventilated in synchronised intermittent mandatory ventilation mode set to deliver a tidal volume of 250 ml and respiratory rate of 12 breaths.min−1 following intravenous sedation with fentanyl 50 μg and midazolam 1 mg.
A lateral cervical spine radiograph demonstrated an increased anterior atlas-dens interval measuring 12 mm and a decreased posterior atlanto-dental interval measuring 12 mm (Fig. 1). Magnetic resonance imaging showed compression of the spinal cord at the craniovertebral junction and upper cervical level, with abnormalities of the spinal cord (Fig. 2). A diagnosis of anterior, non-rotatory, atlanto-axial subluxation with cord compression at the level of the cervical spine was made and the patient underwent posterior approach cervical spine fixation surgery. The child had a slow, but complete, recovery of motor power over the next seven months. He was weaned off ventilatory support and at the time of writing requires occasional bilevel positive airways pressure support (BIPAP) at night (inspiratory:expiratory positive airways pressure ratio of 15:5) owing to sleep-induced hypoventilation and hypercapnia.
Following a discussion with the relatives, it became apparent that, before surgery, the patient could undertake routine activities, but had complained of lethargy, was easily tired and had failed to gain weight or height over the previous two years. He had difficulty climbing stairs and lifting heavy objects as well as persistent, although mild, neck pain. A consultation had been sought with a paediatrician and the symptoms attributed to mild failure to thrive due to tonsillar disease. His neurological examination had demonstrated muscle wasting and mild weakness of all four limbs, hyper-reflexia and bilateral extensor plantar responses. Cardiovascular and respiratory examinations were reported as normal.
This report describes the progress of a child who developed acute neurological impairment due to atlantoaxial subluxation following an apparently uneventful adenotonsillectomy. In retrospect, there was pre-existing atlanto-axial instability as evidenced by muscle wasting. However, the condition remained undetected pre-operatively, probably because the symptoms (lethargy, tiredness and mild neck pain) were mistakenly attributed to recurrent tonsillitis; children with sleep-disordered breathing and recurrent tonsillitis are recognised as having relatively poor general health and failure to thrive . There were no obvious neurological deficits; hence the possibility of a co-existing neurological disease was not considered nor evaluated during the pre-operative assessment. Exaggerated head or neck movements to facilitate laryngoscopy and tracheal intubation, or hyperextension of the head during surgery (the Rose position) at some point resulted in atlantoaxial subluxation and acute neurological deterioration.
Failure to detect atlanto-axial instability may result in critical, and potentially fatal, atlantoaxial subluxation, due to compression of the cervical spinal cord by the odontoid process of the axis (dens) or by the posterior arch of the atlas. Intra-operatively, there is a risk of severe neurological injury due to flexion, hyperextension or excessive lateral rotation of the neck during airway control, surgical positioning or during transfer [2-4]. Quadriparesis and even sudden death have been reported . The ‘sniffing the morning air’ position, used for laryngoscopy and tracheal intubation, is particularly associated with an increased risk of atlantoaxial subluxation .
Although our patient had symptoms and signs that, in retrospect, were indicative of underlying pathology, the possibility of atlanto-axial instability was overlooked by both the paediatrician and the anaesthetist. We wish to highlight that atlanto-axial instability is diverse in its clinical presentation and can range from overt neurological deficits to mild, non-specific symptoms, or may even be asymptomatic [2, 3, 5]. An important warning sign, observed in 85% of children, is the presence of neck pain and occipital headaches, which radiate to the posterior vertex . A history of restricted neck movements, persistent neck tilt (torticollis), bowel and/or bladder involvement, clumsiness, tiredness during everyday activity or changes in gait, such as development of ataxia, are particularly suggestive of an underlying craniovertebral abnormality . Patients may have sensory defects in the hands or feet; in children, this may be recognised by observing the constant rubbing of affected limbs . They may also have associated stigmata of craniovertebral anomalies, such as a short neck, low hairline, facial asymmetry, polysyndactyly, a high arched palate and pes cavus [5, 6]. In these patients, the anaesthetist should suspect cervical spinal cord compression and actively seek signs of mixed upper and lower motor neurone deficits, such as muscle wasting, spasticity, sensory deficits, hyper-reflexia, clonus and extensor plantar reflexes [2, 6]. Patients with suggestive symptoms and signs warrant a cervical spine radiograph and neurosurgical referral for further evaluation.
Radiological evaluation is essential for diagnosis and to assess the severity of the disease, because many patients have only mild clinical features, despite severe cervico-medullary cord compression [2, 3]. A measured distance between the posterior surface of the anterior arch of the atlas and the anterior surface of the dens (anterior atlanto-dental interval) > 4.5 mm in children and 3.0 mm in adults on a lateral cervical spine radiograph suggests atlantoaxial subluxation; compression of the cervical spinal cord always occurs when this distance exceeds 9.0 mm [7, 8]. The distance between the posterior surface of the dens and the anterior surface of posterior arch of the atlas posterior atlanto-dental interval directly assesses the ‘space available for the cord’ within the spinal canal and is a good predictor for potential neurological compromise . A posterior atlanto-dental interval < 14 mm is thought to be associated with a fivefold increase in the risk of neurological dysfunction compared with those having a distance > 14 mm. This increases by up to ten fold in patients with co-existing upper cervical cord or brainstem compression .
Our patient had delayed recovery from anaesthesia associated with respiratory distress and quadriparesis. Two conditions can result in a similar clinical picture and need to be excluded. Children undergoing adenotonsillectony for sleep-disordered breathing are known to have an increased incidence of prolonged emergence and peri-operative respiratory complications although this is not usually associated with neurological deficits . Grisel's syndrome is an important, although rare, condition reported following adenotonsillectomy in children and is characterised by non-traumatic rotatory subluxation of the atlanto-axial joint following peripharyngeal inflammation . Patients usually present with torticollis, adopt a so-called ‘cock robin’ head position with restricted, painful neck movements, but have minimal or no neurological deficits. The condition responds well to conservative management . In contrast, our patient had a non-rotatory atlantoaxial subluxation with severe neurological deficits, that required surgical intervention.
In conclusion, patients with atlanto-axial instability may be asymptomatic or have minimal clinical features despite severe cervical cord compression. The condition may remain undetected or be mistakenly attributed to another disease process. Failure to detect atlanto-axial instability may result in serious neurological injury due to the development of subluxation during head and neck manipulation for airway control or surgical positioning under anaesthesia. A lateral cervical spine radiograph should be performed in patients with positive clinical signs to diagnose and assess the potential for neurological compromise. A neurosurgical opinion should be sought for definitive diagnosis and advice on management.
Published with the written consent of the patient's parent.
No external funding and no competing interests declared.