Patients and Methods
In total 192 children (97 female) with a facial PWS were seen sequentially between March 2011 and January 2013 in the paediatric dermatology and neurology departments at Great Ormond Street Hospital for Children. This cohort included both new patients and follow-up patients. As this is a tertiary referral centre the cohort included a much higher percentage of children with SWS than would be seen in the general population of children with PWS; however, we considered that this may improve the power of our statistical analysis of phenotypic associations. We were not aiming to document the incidence of SWS in a population of patients with PWS.
Hospital notes, radiological results (MRI) and professional high-resolution photographs of these patients were reviewed retrospectively. Clinical data collected were age, sex, cutaneous phenotype, presence of glaucoma, seizures and abnormal neurodevelopment, defined as any degree of motor or cognitive impairment on formal assessment. Facial PWSs were classified using the traditional method based on the sensory branches of the trigeminal nerve (V1, V2, V3) (Fig. 1) and whether they were in a unilateral or bilateral distribution. A second classification was also performed by dividing up the face into eight areas on each side, and indicating which were affected. These areas were the central forehead, lateral forehead, upper eyelid, lower eyelid, maxillary area, mandibular area, ear (where visible) and chin. Scalp involvement was not classified, as the majority of the photographs did not show this adequately.
(a) Distribution of the three branches of the trigeminal nerve. (b) Distribution of the 'forehead', defined as any part of the forehead from the midline to an imaginary line between the outer canthus of the eye and the top of the ear including the upper eyelids. Figure adapted from Anatomy of the Human Body.36
Adverse outcome measures were (i) clinical: seizures, abnormal neurodevelopment and glaucoma; and (ii) radiological: abnormal MRI. Absence of adverse outcome measures was recorded only where definite negative clinical information was documented, rather than by assumption (for example absence of glaucoma was recorded only where a normal ophthalmological examination had occurred). Statistical analysis of the association between the cutaneous phenotype variables and outcome measures was by multivariate logistic regression. For calculation of odds ratios for the effect of involvement of the forehead on outcome measures, 1 was added to each group to correct for a value of 0 in one cell.
The British Journal of Dermatology. 2014;171(4):861-867. © 2014 Blackwell Publishing