Mild Grisel Syndrome: Expanding the Differential for Posttonsillectomy Adenoidectomy Symptoms

Discussion

Grisel syndrome is the atraumatic rotary subluxation of the atlantoaxial joint, specifically, the atlas (C1 vertebra) rotates to a fixed, nonanatomic position while the axis (C2 vertebra) remains in normal alignment in relation to the remainder of the spinal column. The subluxation occurs in the absence of ligamentous injury but is associated with an increase in ligamentous laxity.⁴ The atlas is a ring-shaped vertebra with 2 lateral masses connected by anterior and posterior arches; it lacks a spinous process unlike other vertebrae. It articulates with the skull by means of the 2 articular facets on the superior aspect of the lateral masses. Articulation with the axis occurs at 3 sites: 2 articular facets on the inferior portion of the lateral masses of the atlas and a facet for the dens on the posterior portion of the anterior arch. The dens projects superiorly from the body of the axis and is bound posteriorly by the transverse ligament of the atlas.⁵

The degree of subluxation seen in Grisel syndrome correlates to the disease severity and is classified by the Fielding and Hawkins (FH) system (Table). This system accounts for the distance from the atlas to the dens (atlantodens interval) and the relative asymmetry of the atlantoaxial joint.⁶ In a normal adult, the upper limit of normal for the atlantodens interval is 3 mm, whereas this distance increases to 4.5 mm for the pediatric population.⁷ Type I (FH-I) involves rotary subluxation alone without any increase in the atlantodens interval; in FH-II, that interval has increased from normal but to no more than 5 mm. FH-I and FH-II are the most encountered and are not associated with neurologic impairment. In FH-III, neurologic deficits can be present, and the atlantodens interval is increased to > 5 mm. Different from FH-II and FH-III in which anterior dislocation of the atlas with reference to the dens is observed, FH-IV involves a rotary movement of the atlas with concurrent posterior displacement and often involves spinal cord compression.⁶

Subluxation and displacement without trauma are key components of Grisel syndrome. The 2-hit hypothesis is often used to explain how this can occur, ie, 2 anomalies must be present simultaneously for this condition to develop. First, the laxity of the transverse ligament, the posterior wall of the dens, and other atlantoaxial ligaments must be increased. Second, an asymmetric contraction of the deep erector muscles of the neck either abruptly or more insidiously rotate and dislocate the atlas.⁸ The pathophysiology is not exactly understood, but the most commonly held hypothesis describes contiguous spread of infection or inflammatory mediators from the pharynx to the ligaments and muscles described.⁶

Spread could occur via the venous system. The posterior superior pharyngeal region is drained by the periodontoidal venous plexus; the connections here with the pharyngovertebral veins allow for the embolization of infectious or other proinflammatory material to the prevertebral fascia. These emboli induce fasciitis and subsequent aberrant relaxation of the ligaments. In reaction to the inflammation or increased laxity, contiguous muscles of the deep neck contract and freeze the joint out of anatomic alignment.⁴

The abnormal alignment is apparent grossly as torticollis. Most broadly, torticollis describes an anomalous head posture due to involuntary muscle contractions of neck muscles and specifically describes chin deviation to the side. The antecollis and retrocollis subtypes of torticollis describe forward flexion and backward extension of the neck, respectively.⁷ Torticollis (broadly) is the most frequently reported condition of those found to have Grisel syndrome (90.7%); other common presenting conditions include neck pain (81.5%) and neck stiffness (31.5%). Fever is found in only 27.8% of cases. Pediatric patients (aged ≤ 12 years) are the most commonly affected, accounting for 87% of cases with an observed 4:1 male to female predominance.^7,8 Symptoms begin most often within the first week from the inciting event in 85% of the cases.⁸ Head and neck surgery precedes up to 67% of cases, and infectious etiologies largely account for the remaining cases.⁷ Of the postsurgical cases, 55.6% had undergone T&A.⁸

Although anomalous head posture or neck stiffness following T&A would be of great clinic concern for Grisel syndrome, radiographic studies play a confirmatory role. CT scan is used to evaluate the bony structures, with 3D reconstruction of the cervical spine being most useful to determine the presence and degree of subluxation.⁸ Magnetic resonance imaging also aids in diagnosis to evaluate ligamentous structures in the area of concern as well as in the evaluation of spinal cord compression.⁶ Laboratory tests are largely unhelpful in making or excluding the diagnosis.⁸

If Grisel syndrome is suspected, both the original surgeon (if preceded by surgery) and the neurosurgical team should be consulted. Although no widely adopted guidelines exist for the management of this rare disease, general practice patterns have emerged with the degree of intervention predictably correlating to disease severity. FH-I is usually treated with nonsteroidal anti-inflammatory drugs and muscle relaxants with or without a soft cervical collar. For FH-II, closed reduction and immobilization in a stiff cervical collar is recommended. If no neurologic defect is present, FH-III is treated with bed rest, a period of inline cervical traction, and subsequent immobilization. FH-III with neurologic sequelae and all FH-IV necessitate emergent neurosurgical consultation.⁴ Surgical intervention is a last resort but is required in up to 24.1% of cases.⁸

Antibiotic therapy is not routinely given unless clear infectious etiology is identified. No standard antibiotic regimen exists, but coverage for typical upper respiratory pathogens likely suffices. Empiric antibiotic therapy is not recommended for all causes of Grisel syndrome, ie, when the underlying cause is not yet elucidated.⁶ One case of Grisel syndrome occurring in the setting of cervical osteomyelitis has been described, though, and required prolonged IV antibiotics.³ Physical therapy is recommended as adjunct with no limitations for range of motion save for that of the patient’s individual pain threshold.⁴

Possibly attributable to waxing and waning ligamentous laxity and strength of the neck muscle contraction, the atlantodens interval and the degree of subluxation can change, making Grisel syndrome dynamic. As such, the FH classification can change, necessitating more or less aggressive therapy. A neurologic evaluation is recommended at least every 2 weeks after the diagnosis is made. If initial identification or recognition of known disease progression is delayed, serious complications can develop. Acutely, spinal cord compression can lead to quadriplegia and death; more insidious complications include reduced neck mobility, dysphonia, and dysphagia.⁴ As serious, life-threatening complications can arise from Grisel syndrome while good functional outcomes can be achieved with timely and appropriate treatment, the clinician should be inspired to have a high clinical suspicion for this syndrome given the right context.

Conclusions

The patient experienced a desirable outcome with minimal, conservative treatment. As such, the pathology in this case was likely attributed to the mildest form of Grisel syndrome (FH-I). The follow-up was reassuring as well, revealing no worsening or progression of symptoms. The initial evaluation in this case was limited by the inadequacy of the CT scan. Motion artifact in the pharynx prevented the definite exclusion of deep space infection, while the rotation of the head in combination with motion artifact in the cranial-most portions of the vertebral column made determining alignment difficult. One clear axial image, though, does show rotation of the atlas (Figure 2). The uncertainty at the end of our workup prompted surgical consultation, not, admittedly, concern for Grisel syndrome. Awareness of this disease entity is nevertheless important and clinically relevant. Early identification and treatment is associated with decreased morbidity and improvement in long-term functional outcomes.⁶ Despite its rarity, the clinician should consider Grisel syndrome in any pediatric patient presenting with neck stiffness following the commonly performed T&A.