Congenital Fusion of C6 and C7 Vertebra–A Case Report

During osteology demonstration classes for 1^st year MBBS medical students fused cervical sixth and seventh vertebra were found having completely fused bodies [Table/Fig-1]. However, the bodies were partially fused posteriorly leaving a small gap on left side. Superior surface of sixth cervical vertebrae had uncal process for inferior surface of body of fifth vertebra. Inferior surface of seventh cervical Inferior surface of seventh cervical vertebra was flat. Pedicle, laminae and foramina transversarium were not fused on both the sides, Intervertebral foramina were patent. The inferior articular facet of C6 and superior articular facet of C7 were partially fused [Table/Fig-2].

[Table/Fig-1]:

Shows fusion of body of sixth and seventh vertebra. BC-6 body of sixth vertebra, BC7-body of seventh vertebra. AF-Anterior foramen

[Table/Fig-2]:

Shows partially fused articular facets [AF], Spines C6 and C7 vertebra, Foramina transversarium [FT]

In Fused cervical vertebrae, the fusion may be either congenital or acquired [1]. Congenital fusion of cervical vertebrae (CFCV) is one of primary malformations of chorda dorsalis [2]. The most important differential diagnosis in CFCV is decreased AP diameter of the vertebra and individual measurements of the two vertebral bodies’ height are equal to the two fused vertebrae’s height including the intervertebral disc [1]. Diseases like tuberculosis, juvenile rheumatoid arthritis and trauma is generally associated with acquired FCV [1]. In this case vertebral bodies were normal. We didn’t observe any degenerative in the vertebrae, suggesting it might be congenital.

Common site of fusion of cervical vertebrae is at C2-C3 with an incidence of 0.4% to 0.7% with no sex predilection [3]. According to the frequency of block vertebrae, the order is C2-C3, C5-C6, L4-L5 and any segment of thoracic spine block vertebrae [3].

Vertebral column starts developing during 3^rd week with segmentation of paraxial mesoderm forming somites. Failure of normal segmentation of embryological spines may lead to fused vertebrae or block vertebrae [4]. Disturbance of PAX-1 gene expression may lead to vertebral fusion anomalies [5].

Although, FCV may be silent; in advanced age it causes degenerative changes in non segmented cervical regions and secondarily, it leads to hyper mobility and degenerative arthritis above and below the fused cervical region [6,7]. Defects in development of occipital and cervical somites and effect of environment, genetic factors during 3^rd week of conception may lead to such fusion of vertebra [8,9]. Fusion of cervical vertebrae may cause shortening of cervical spine, lateral prominence of trapezius gives webbed appearance of neck, limited neck motion, lowered hair line, osseous malformation (scoliosis, kyphosis and torticollis) may lead to signs of peripheral nerve irritation such as pain, burning sensations and cramp or signs of nerve compression such as hypoaesthesia/anaesthesia, weakness/paralysis, fibrillations and reduced deep reflexes [10].

Awareness of these anomalies may reduce anaesthetic risk during intubation with neck extension [11]. [Table/Fig-3] shows reported cases of fusion of cervical vertebrae in different population. Early diagnosis of these anomalies can help in progression of degenerative process by motivating the patient to change their life style like avoiding undue trauma, extension and rotational maneuvers which may place the spinal cord and vertebral artery at risk [3].

Fusion of C6 and C7 restricts the movements of the neck and may also compress the nerves. Knowledge of such anomalies is important for anaesthesiologists during intubation and also for orthopaedicians, neurosurgeons and surgeons during surgeries of the neck.

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