TABLE 96.2 EXAMPLES OF PRIMARY AND SECONDARY MICROCEPHALY Primary microcephaly Genetic Environmental Secondary microcephaly Isolated Autosomal recessive Autosomal dominant X-linked Syndromic, e.g., Aicardi syndrome Cornelia de Lange Chromosomal Trisomies Microdeletions Structural anomalies, e.g., Holoprosencephaly Anencephaly Intrauterine Infections TORCH Hemorrhage/Thrombosis Teratogens Drugs Irradiation Vascular accidents Placental infarctions Hypoxia–ischemia Maternal disease Malnutrition Phenylketonuria Inborn errors of metabolism Phenylketonuria Galactosemia Environmental Irradiation Heavy metal poisoning Inborn errors of metabolism Infections From Von der Hagen M, Pivarcsi M, Liebe J, et al Diagnostic approach to microcephaly in childhood: a twocenter study and review of the literature Dev Med Child Neurol 2014;56(8):732–741 Copyright © 2014 Mac Keith Press Reprinted by permission of John Wiley & Sons, Inc Abnormalities of Head Shape Craniosynostosis Craniosynostosis occurs because of premature closure of one or more of the cranial sutures, resulting in an abnormality in the shape of the head perpendicular to the closed suture It is occasionally accompanied by facial dysmorphism In cases where multiple sutures are involved, infants may develop increased intracranial pressure and neurocognitive impairment The incidence of craniosynostosis is approximately per 2,000 live births; sagittal synostosis being the most common (40% to 55%) Primary craniosynostosis occurs when there is primary closure of a suture and may be nonsyndromic (isolated) or syndromic (with associated anomalies as in Apert, Crouzon, and Pfeiffer syndromes) Secondary craniosynostosis is caused by a systemic disorder (e.g., thalassemia) Pathogenesis is thought to be multifactorial but fundamentally related to premature signaling of the dura to the sutures to close prematurely before completion of brain growth Fibroblastic growth factor receptor (FGFR1 and 2) mutations have been implicated in both the nonsyndromic and syndromic types Diagnosis of craniosynostosis is made on clinical appearance of the shape ( Fig 96.22 ) Palpation reveals a ridge along the closed suture and compensatory bossing, or deformity on the contralateral side In brachycephaly syndromes, the orbit is shallow with proptosis of the eyes, and there is a characteristic “parrot beak” nose (short, stubby, and upturned) Physical examination may reveal polysyndactyly (Apert syndrome) or broad toes and thumbs (Pfeiffer syndrome) Skull radiographs and CT scan are needed to delineate single versus multiple suture involvement Corrective surgery should ideally occur before months of age Surgery allows remodeling of the skull, relieves cranial pressure, and improves cosmetic outcome Prognosis depends on the type of craniosynostosis, the timing of the surgery, and the number of sutures or facial bones involved All syndromic craniosynostosis usually involve the coronal sutures Corrective surgeries are directed at expansion of the anterior and posterior cranial vaults and are more complex, requiring a dedicated multidisciplinary craniofacial team Deformational Plagiocephaly Deformational plagiocephaly applies to asymmetry of the cranium caused by flattening of one side of the occiput Incidence has increased since 1992, after institution of the “back to sleep” campaign Constant mechanical pressure applied to one side of the head (preferential turning or sleeping on the same side) results in flattening of that side so that the head assumes a parallelogram shape (flattening of the occiput with bossing of the ipsilateral frontal pole) Contributing mechanical forces include in utero forces (bicornuate uterus or twin pregnancy), or postnatal conditions, such as preferential head turning torticollis or vertebral anomalies At birth, infants have round heads but will develop this shape after a few months The ipsilateral ear is displaced anteriorly but both ears are in the same horizontal plane Deformational plagiocephaly should be differentiated from lambdoid suture synostosis, which occurs at birth, with frontal bossing on the contralateral side and posterior and downward displacement of the ears Skull radiography is usually not necessary if the baby has a typical history and physical examination Treatment is nonsurgical Parents are encouraged to alternate head position of the infant and allow infants 30 minutes of tummy time while awake to prevent the occurrence of deformational plagiocephaly Neck exercises to encourage range of motion have also been found to be helpful in combination with positioning Alternately, infants with severe deformational plagiocephaly may benefit from helmets, or head bands worn during the day Corrective surgery is rarely needed for those who not respond to nonsurgical measures Prognosis is good and the shape improves after infants gain head control and begin to sit FIGURE 96.22 Morphologic types of craniosynostosis Diagrammatic views of different morphologic types of craniosynostosis are shown in the center of the figure The premature closed suture is marked as a bold line The sutures involved determine the shape of the skull The diagrammatic view of each synostosis type is matched with the corresponding radiologic findings The fused suture is seen as a hypertrophic keel or ridge on the x-rays (Reprinted with permission from Paul Mongan P, Soriano III SG, Sloan TB, et al Practical Approach to Neuroanesthesia Philadelphia, PA: Lippincott Williams & Wilkins; 2013.)