Cervical spine MRI was done for a young male patient, for evaluation of neck pain. Incidentally there was right hemifacial hyperplasia, which was noticed by the patient since childhood.
Right masseter showed increased thickness ( Compare with the left).
Right IJV is seen enlarged.
Right parotid gland is also seen enlarged.
Depending on involvement of soft tissues, teeth, and bones, Rowe further classified hemifacial hypertrophy into (a) true hemifacial hypertrophy and (b) partial hemifacial hypertrophy.
True hemifacial hypertrophy exhibits unilateral enlargement of all tissues, teeth, bones, and soft tissues, characterized by viscerocranial enlargement, bounded by frontal bone superiorly (sparing the eye), inferior border of the mandible inferiorly, midline medially, and ear including the pinna laterally.
In partial hemifacial hypertrophy not all structures are enlarged to the same degree or limited to one structure. The term hyperplasia is more precise histologically, as all tissues show an increase in the number of cells rather than an increase in cell size.
Hemifacial hyperplasia is associated with a wide variety of abnormalities such as thickened skin and hair on the involved side, excessive secretion of sebaceous and sweat glands, and vascular and pigmentary defects of the affected side. Different texture and colour variance of ipsilateral scalp hair have also been reported. In addition skeletal abnormalities such as macrodactyly, polydactyly, syndactyly, ectrodactyly, scoliosis, tilting of pelvis, and clubfoot have also been described.
Central nervous system involvement in the form of cerebral enlargement, epilepsy, strabismus, and mental retardation in 15–20% of patients has been reported in the literature. Ipsilateral pinna and pupil may be enlarged, but an increase in size of the inner ear or globe of the eye has not been reported. Occurrence of small exostoses of the posterior auditory canal has also been reported.
Adrenal cortical carcinoma, nephroblastoma (Wilm’s tumour), and hepatoblastoma can be occasionally associated with this disorder. Genitourinary system disorders, such as hypospadias, cryptorchidism, and medullary sponge kidney, were also noted occasionally.
Other bony conditions that may result in hemifacial enlargement like FD, Paget's etc are usually associated with narrowing of the skull base foramina, but hemifacial hyperplasia usually result in their widening.
References
R. A. Pollock, M. Haskell Newman, A. R. Burdi, and D. P. Condit, “Congenital hemifacial hyperplasia: an embryologic hypothesis and case report,” Cleft Palate Journal, vol. 22, no. 3, pp. 173–184, 1985.
N. H. Rowe, “Hemifacial hypertrophy—review of the literature and addition of four cases,” Oral Surgery, Oral Medicine, Oral Pathology, vol. 15, no. 5, pp. 572–587, 1962.
Bansari A. Bhuta, Archana Yadav, Rajiv S. Desai, Shivani P. Bansal, Vipul V. Chemburkar, and Prashant V. Dev, “Clinical and Imaging Findings of True Hemifacial Hyperplasia,” Case Reports in Dentistry, vol. 2013, Article ID 152528, 7 pages, 2013. doi:10.1155/2013/152528