Non-traumatic rotatory subluxation of C1 on C2 (Grisel\'s syndrome)

Clinical History

Young boy with 3-month history of progressive neck pain and stiffness. There was no history of trauma but a preceding nonspecific upper respiratory tract infection was described. On clinical examination there was evidence of torticollis and the patient’s neck was fixed in position. Imaging investigations were arranged.

Imaging Findings

Radiographs (Fig. 1a and 1b) demonstrate a slight tilt of the head and marked increase of the atlantodental distance at 7 mm indicating C1-C2 instability. Further evaluation with CT (Fig. 2a-c) demonstrates the presence of rotatory subluxation of the atlas with respect to the axis. The tip of the Peg articulates with the left occipital condyle. The marked increase in atlantodental distance at 7 mm corresponds with a Fielding type III subluxation. 3D reconstruction (Fig. 3) assists in the visual demonstration of the abnormalities. MR imaging (Fig. 4 a-c) allows improved contrast of the soft tissue structures and demonstrates an intact transverse ligament. Fig. 5a and 5b demonstrate the appropriate positioning of the patient while undergoing therapeutic external fixation.

Discussion

Grisel's syndrome or rotatory subluxation of C1 on C2 in the absence of trauma occurs predominantly in children. The main associative causes are infection predominantly URTI, post surgery particularly adenotonsillectomy and other ENT operations less commonly. The pathogenesis is unclear but it is believed to arise from peripharyngeal hyperaemia secondary to inflammation or infection, which causes ligamentous distension and laxity. [1]

Symptoms are typically those of torticollis, neck pain and stiffness. A background history of recent/ongoing pharyngeal infection or recent head/neck surgery is often established. Delayed diagnosis can result in significant morbidity and cases of associated mortality have been described.[1] The diagnosis is rare and suspected based on clinical history and examination findings. Imaging can subsequently confirm the diagnosis.

Plain radiographic findings include soft tissue swelling, facet joint asymmetry and an increase in the atlantodental distance. The atlantodental distance is normally up to 3 mm in adults and 4.5 mm in children [2], distances greater than those described indicate subluxation. CT will accurately define the degree of subluxation and rotation. In subtle cases dynamic CT with movement of the neck to left and right can be used to demonstrate loss of normal rotation. MR imaging can complement CT by defining ligamentous structures, it can be impractical in younger patients and is not required for the diagnosis.

A classification system for non traumatic rotatory subluxation has been described by Fielding and Hawkins. [3]

Type I: Rotatory fixation without anterior displacement of the atlas <3mm
Type II: Rotatory fixation with anterior displacement of the atlas 3-5 mm
Type III: Rotatory fixation with anterior displacement of the atlas >5mm
Type IV: Rotatory fixation with posterior displacement of the atlas.

The more severe the abnormality i.e. type III and IV, the higher the risk of neurological complications related to cord compression.

Management is aimed at reducing the subluxation and treating any underlying infection with antibiotics. Less severe cases are treated conservatively with bedrest, muscle relaxants, immobilisation and physiotherapy. External fixation and potentially surgical artrodesis may be required for more advanced cases and those which fail to respond to conservative measures. [1, 2]

Teaching Points

The condition is rare, occurs predominantly in the paediatric population and clinical suspicion should be aroused by presence of torticollis and relevant history of infection or surgery.

Diagnosis can be made on plain film but CT is the imaging modality of choice where there is a high clinical suspicion.

Differential Diagnosis List

Final Diagnosis

Non-traumatic rotatory subluxation of C1 on C2 (Grisel's syndrome)

URL:	https://www.eurorad.org/case/9744
DOI:	10.1594/EURORAD/CASE.9744
ISSN:	1563-4086