Fractures of the first cervical vertebra are infrequent findings in trauma victims. Furthermore, congenital abnormalities of the craniocervical junction are incidental findings on routine x ray examinations of the cervical spine. However, in trauma examination, some deficiencies may result in erroneous interpretation.^1,2

Thalassaemia, which belongs to a group of chronic, familial haemolytic anaemias, is common among the populations of the countries bordering the Mediterranean Sea. It is characterised by abnormality in the balance of production of the α and β-haemoglobin chains. Thalassaemia minor is asymptomatic in most cases, so the resultant anaemia could be yet another possible pitfall in the emergency management of trauma, as it may mimic major blood loss.

We report a 16 year old girl with suspected traumatic injury of the cervical spine who had complete absence of the posterior arch of the atlas as confirmed by magnetic resonance (MR) imaging and, in addition, as a further diagnosis, thalassaemia minor. To our knowledge, it is the first report of the co-occurrence of these two congenital abnormalities.

CASE REPORT

A 16 year old girl was cycling on a staircase on her bike when she fell on the left side of her face and suffered multiple scratches. On admission, she complained of neck pain. She had slightly impaired active flexion, extension, and rotation of the head, primarily due to the pain. There were no neurological deficits. A routine blood sample revealed haemoglobin 9.8 mg/dl. At first major injury was suspected, but on clinical examination this was not confirmed.

There was a void evident in the posterior part of the craniocervical junction in the plain x rays of the cervical spine (fig 1). Initially, fracture of the atlas was suspected, although no fragment was seen. A detailed history revealed no known cervical abnormalities but a kind of Mediterranean anaemia and that the patient’s father originated from Italy.

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Figure 1

 Lateral x ray of the cervical spine showing a complete absence of the posterior arch of the atlas.

The patient was admitted for further clinical observation and examination. Additional MR imaging of the cervical spine revealed a congenital deficiency of the posterior arch of the atlas without a posterior tubercle and ruled out a fracture or any other structural injury (fig 2). Laboratory investigations, including haemoglobin electrophoresis and blood smear revealed the following results (laboratory reference values in parenthesis): haemoglobin 9.8 mg/dl (14.0–18.0); MCH 29 pg (29.0–34.0); MCV 85 fl (86.0–100.0); serum iron 130 μg/dl (40–130); HbA₂ 6.3% (2–3%); HbF 3.1% (0.8–2%); HbA₁ 90.6% (95–98%). Thus the presence of a hypochromic, microcytic anaemia led to a diagnosis of β-thalassaemia.

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Figure 2

 Magnetic resonance scan of the atlas—missing posterior arch.

DISCUSSION

Perichondral ossification of the posterior arch of the first vertebral body starts from two centres in the lateral masses and proceeds to the midline.³ Fusion normally occurs at three to five years of age, and incomplete fusion persists in 3–5%.⁴ Occasionally, ossification starts from a separate posterior centre, fusing with the lateral masses to form the posterior arch and leading to the development of a posterior tubercle.^5–7 Larger defects of the posterior arch are rare; some authors have reported an incidence of less than 1%. The underlying embryological basis is commonly believed to be a local mesenchymal defect leading to lack of chondrification.^7,8

Currarino et al⁸ proposed an anatomical classification of the defects of the posterior atlas, modified from Von Torklus and Gehle⁵:

• Type A—failure of the posterior midline fusion of the two hemiarches

• Type B —unilateral cleft

• Type C—bilateral clefts

• Type D—total absence of the posterior arch with a persistent posterior tubercle

• Type E—total absence of the posterior arch with missing posterior tubercle.

According to this classification, the present patient has a rare type E abnormality. A hypertrophic spinous process of the axis (C2) is described occasionally in type E abnormalities. Our patient also had this (fig 1).

Hereditary factors may contribute to these anomalies, but the frequency of heredity is not known. Motatenau et al⁹ and Currarino et al⁸ reported an affected mother and daughter, and mother and son, respectively. Our patient’s father had thalassaemia minor as well as the patient herself, but we were unable to obtain informed consent for further x ray examination of the cervical spine or laboratory examination.

In most reports, the lesion was discovered incidentally in asymptomatic patients.^10,11 In others, the patients had complained of neck discomfort and x ray examination of the cervical spine had revealed incomplete arches.^7,12–14 Sporadic neurological deficits have been described. To our knowledge, however, no permanent neurological deficits such as paralysis have been reported. Richardson et al¹⁵ reported a patient with an incomplete absence of the posterior arch who had intermittent quadriparesis after hitting his head against a car door, and who recovered completely with resolution of any neurological symptoms. Thalassaemia major (Cooley’s anaemia) sometimes leads to bony abnormalities such as “hair on end” appearance of the skull bone, but no cervical spine abnormalities have been reported so far.

CONCLUSION

It is essential to be aware of both conditions—deficiency of the posterior arch of the atlas and thalassaemia minor—as both anomalies may lead to false diagnosis, especially in trauma victims. Of course, the aetiopathogenetic relation cannot be proved in this case. When treating trauma victims it is important to have both abnormalities in mind, in order not to mistake slightly injured for severely injured patients.