The Abnormal Fontanel JOSEPH KIESLER, M.D., and RICK RICER, M.D., University of Cincinnati College of Medicine, Cincinnati, Ohio

Home , Coronal suture, Craniotabes, Fontanelle, Lambdoid suture, Sagittal suture

PROBLEM-ORIENTED DIAGNOSIS

The diagnosis of an abnormal fontanel requires an understanding of the wide variation of normal. At birth, an infant has six fontanels. The anterior fontanel is the largest and most important for clinical evaluation. The average size of the anterior fontanel is 2.1 cm, and the median time of closure is 13.8 months. The most common causes of a large anterior fontanel or delayed fontanel closure are achondroplasia, hypothyroidism, Down syndrome, increased intracranial pressure, and rickets. A bulging anterior fontanel can be a result of increased intracranial pressure or intracranial and extracranial tumors, and a sunken fontanel usually is a sign of dehydration. A physical examination helps the physician determine which imaging modality, such as plain films, ultrasonography, computed tomographic scan, or magnetic resonance imaging, to use for diagnosis. (Am Fam Physician 2003;67:2547-52. Copyright© 2003 American Academy of Family Physicians)

Members of various xamination of a newborn’s fon- family practice depart- tanels offers the physician a win- Anatomy of the Fontanels ments develop articles dow into the infant’s developing Fontanels are the fibrous, membrane-cov- for “Problem-Oriented Diagnosis.” This article brain and general state of health. ered gaps created when more than two cranial is one in a series from The word “fontanel” is derived bones are juxtaposed, as opposed to sutures, the Department of Efrom the Latin fonticulus and the Old French which are narrow seams of fibrous connective Family Practice at the fontaine, meaning a little fountain or spring.1-3 tissue that separate the flat bones of the skull. University of Cincinnati The normal fontanel varies widely in shape A newborn has six fontanels (Figure 1): the College of Medicine. Guest coordinator of and time of closure. The incidence of abnor- anterior and posterior, two mastoid, and two 4 the series is Susan mal fontanel differs, depending on the abnor- sphenoid. The rhomboid-shaped anterior Montauk, M.D. mality and cause. fontanel, located at the juncture of the two

Anterior fontanel Parietal bone Metopic suture

Coronal suture Anterior fontanel . Frontal bone . . Squamous suture Frontal bone . . . Sphenoid Parietal . . Coronal fontanel bone . suture Posterior . fontanel ...... Occipital Sagittal Zygomatic . bone suture bone . Lambdoid Posterior . structure fontanel . .

Temporal Mastoid fontanel Sphenoid bone Lambdoid suture bone Occipital bone ILLUSTRATIONS BY CHRISTY KRAMES

FIGURE 1. (Left) Lateral view of the newborn skull. (Right) Superior view of the newborn skull. Redrawn with permission after Netter FH. Atlas of human anatomy. Summit, N.J.: Ciba-Geigy, 1994.

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days.8 The newborn’s skull should be evaluated for shape, circumference, suture ridges, and size of anterior and posterior fontanels. Size is cal- Anteroposterior (a) and transverse (b) diameters culated by the average of the anteroposterior 9 a + b and transverse dimensions (Figure 2). = anterior fontanel size 2 The fontanels should be examined while the infant is calm and held in both supine and FIGURE 2. Measurement of the anterior upright positions. In select cases, such as new- fontanel. borns with multiple hemangiomas or heart failure, the anterior fontanel is auscultated to parietal and two frontal bones, is the most detect a bruit, which can indicate an arteri- prominent. The superior sagittal dural venous ovenous malformation.10 Palpation of the sinus is partially situated beneath the anterior fontanel in the upright position may reveal a fontanel. The triangular posterior fontanel is normal, slight pulsation. If the fontanels are located at the junction of the occipital and two closed and intracranial pressure has parietal bones.1,5 increased, percussion produces a “cracked- pot” sound (dull, lacking resonance), known Growth and Development of the Skull as Macewen’s sign. The flat bones of the skull develop as part of Any associated dysmorphic facial features the membranous neurocranium. Needle-like should be noted. Asymmetry of the head is spicules radiate from a primary ossification detected by looking at the infant’s head from center toward the periphery. These irregular above. Head circumference is an important bone islands are remodeled into flattened indicator of brain development and should be sheets of bone by osteoblast and osteoclast monitored over time, especially if a fontanel activity. During fetal and postnatal life, the closes early.6,11 membranous bones enlarge by resorption centrally and by apposition of new layers at IMAGING the edges of the sutures.5 Plain radiographs of the skull are the least Growth of the cranium is triggered by brain expensive way to evaluate the sutures and growth, two thirds of which occurs by two cranial bones, but they are limited by the lack years of age. Except for the metopic suture of mineralization of the neonatal cranium. between the frontal bones, which closes at two Bridging of bone over a suture, an indistinct years of age, the sutures remain open until suture, or sclerosis along the suture margins brain growth ceases in the second decade of indicates fusion. Cortical thinning, widened life.6 Once a suture is fused, growth perpen- sutures, and a beaten-metal appearance dicular to that suture is restricted. Therefore, known as “thumbprinting” are associated fontanel size is influenced by brain growth, with increased intracranial pressure.12 dural attachments, suture development, and If the anterior fontanel is open, ultrasonog- osteogenesis.7 raphy is useful to evaluate ventricular dilata- tion.13 A computed tomographic (CT) scan Examination of the Fontanels can detect a fused suture, dilated ventricles, en- PHYSICAL EXAMINATION larged subarachnoid space, brain size, or an The newborn’s skull is molded during birth. intracranial or extracranial mass.14 Magnetic The frontal bone flattens, the occipital bone is resonance imaging (MRI) can detect cortical pulled outward, and the parietal bones over- and white-matter abnormalities, such as de- ride. These changes aid delivery through the generative diseases, and document the extent birth canal and usually resolve after three to five of calvarial masses. Disadvantages of CT scans

2548 AMERICAN FAMILY PHYSICIAN www.aafp.org/afp VOLUME 67, NUMBER 12 / JUNE 15, 2003 TABLE 1 Conditions Associated with an Enlarged Anterior Fontanel and Delayed Closure

Enlarged Delayed Conditions fontanel closure

Most common Achondroplasia ✓✓ and MRI include cost, the need for sedation, Congenital hypothyroidism ✓✓ 13,15 and, in the case of CT, irradiation. Down syndrome ✓✓ ✓✓ Normal Fontanel Increased intracranial pressure Normal variation ✓✓ POSTERIOR FONTANEL Familial macrocephaly ✓ At birth, the average size of the posterior Rickets ✓✓ fontanel is 0.5 cm in white infants and 0.7 cm Less common 16 in black infants. The fontanel usually is com- Skeletal disorders 10 pletely closed by two months of age. Acrocallosal syndrome (seizures, polydactyly, mental ✓ retardation) ANTERIOR FONTANEL Apert’s syndrome (craniosynostosis, proptosis, hypertension) ✓✓ The key feature of a normal anterior fontanel Campomelic dysplasia (prenatal growth deficiency, large ✓ cranium, bowed legs) is variation. On the first day of an infant’s life, Hypophosphatasia (polyhydramnios, short, deformed ✓✓ the normal fontanel ranges from 0.6 cm to limbs, soft skull) 3.6 cm, with a mean of 2.1 cm.17 Black infants Kenny-Caffey syndrome (hypoparathyroidism, dwarfism, ✓✓ have larger fontanels (1.4 cm to 4.7 cm).16 The macrocephaly) fontanels of full-term and preterm infants are Osteogenesis imperfecta (shortened limbs, wormian ✓✓ calvarial bones) similar in size once preterm infants reach term. The fontanel can enlarge in the first few months Chromosomal abnormalities Trisomy 13 (polydactyly, microcephaly, cleft lip and palate) ✓✓ of life,18 and the median age of closure is 13.8 Trisomy 18 (growth retardation, small cranium, open ✓✓ months. By three months of age, the anterior metopic suture) fontanel is closed in 1 percent of infants; by 12 Congenital infections months, it is closed in 38 percent; and by 24 Rubella (low birth weight, cataracts, “blueberry muffin” ✓ months, it is closed in 96 percent. Anterior skin lesions) fontanels tend to close earlier in boys than in Syphilis (saddle nose deformity, joint swelling, ✓✓ girls; the initial size of the fontanel is not a pre- maculopapular rash) dictor of when it will close.19 Drugs and toxins Aminopterin-induced malformation (craniosynostosis, ✓✓ Abnormal Anterior Fontanel absences of frontal bones, hypertelorism) Fetal hydantoin syndrome (microcephaly, broad nasal ✓✓ LARGE FONTANEL AND DELAYED bridge, hypoplasia of nails) FONTANEL CLOSURE Dysmorphogenetic syndromes A list of the medical conditions associated Beckwith-Wiedemann syndrome (macrosomia, ✓✓ with a large fontanel or delayed fontanel abdominal wall defect, macroglossia) closure can be found in Table 1.20,21 Achon- Zellweger syndrome (high forehead, flat occiput, ✓✓ droplasia, congenital hypothyroidism, Down abnormal ears, hypotonia) Cutis laxa (pendulous skin folds, hoarse cry) ✓✓ syndrome, rickets, and increased intracranial VATER association (vertebral defects, anal atresia, ✓✓ pressure are among the most common condi- tracheoesophageal fistula, renal dysplasia) tions. Otopalatodigital syndrome (frontal bossing, broad ✓ Achondroplasia is an autosomal-dominant terminal phalanges, syndactyly) disorder of the epiphyseal plate cartilage that Miscellaneous results in dwarfism.22 At birth, the infant has Malnutrition (poor weight gain, asymmetric growth) ✓✓ ✓ an enlarged head, low nasal bridge, prominent Hydranencephaly (macrocephaly, thinned skull vault, primitive reflexes preserved) forehead, and shortened extremities, in addi- Intrauterine growth retardation (birth weight less than ✓ 9 tion to a large fontanel. 2 standard deviations below mean) An elevated thyroid-stimulating hormone level on a newborn screening usually detects Information from references 20 and 21. congenital hypothyroidism, but an abnor-

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Most common Chromosomal defects Congenital infections Fetal alcohol syndrome Hypoxic-ischemic encephalopathy mally large anterior fontanel in conjunction Normal genetic variation with an open posterior fontanel can be an Others early sign of the disorder. Myxedema and Autosomal dominant or recessive types growth deficiency are later signs. Dysmorphic syndromes A third fontanel between the anterior and Malnutrition posterior fontanels is associated with hypo- Maternal phenylketonuria thyroidism and Down syndrome.23 Infants Normal variation with Down syndrome often have a single pal- Structural brain defects Universal craniosynostosis mar crease, flat occiput and facies, rounded ears, and slanted palpebral fissures. Information from references 20 and 28. Rickets resulting from vitamin D deficiency rarely occurs in the United States but is one of the five most common childhood diseases in developing nations. Risk factors include such cases is essential to exclude a pathologic breastfeeding without vitamin D supplemen- condition. The fontanel sometimes can be tation, dark skin, and low sunlight exposure. open but difficult to detect during a physical One of the signs of rickets is craniotabes, a examination. Craniosynostosis and abnormal softened outer table of the occipital bone that brain development are associated with a small buckles under pressure, producing a reaction fontanel or early fontanel closure.20 similar to a ping-pong ball indenting and pop- Craniosynostosis is the premature closing ping back out. Craniotabes is not present at of one or more cranial sutures, resulting in an birth but develops over the first few months of abnormal head shape. The condition can be life. Craniotabes can occur normally in pre- idiopathic or caused by hyperthyroidism, mature infants and in children younger than hypophosphatasia, rickets, or hyperparathy- six months.18,24,25 roidism.20 It is also associated with more than Disorders associated with increased intra- 50 syndromes, such as Apert’s, Crouzon’s and cranial pressure that results in an abnormally Pfeiffer’s. The risk of primary isolated cranio- large fontanel or delayed fontanel closure are synostosis is 0.4 per 1,000 live births, and the discussed later in this article. sagittal suture is most commonly involved. Examination at birth of an infant with cra- SMALL FONTANEL OR EARLY FONTANEL CLOSURE niosynostosis might reveal a ridge over a suture Fontanel closure that occurs as early as three or lack of movement along a suture when al- months of age can be within normal limits, but ternating sides are gently pressed. Overriding of careful monitoring of head circumference in sutures from the normal molding process should resolve within the first few days of life.9 Later physical findings in infants with primary craniosynostosis include stunted cranial The Authors growth, increased intracranial pressure, pro- JOSEPH KIESLER, M.D., is an assistant professor and director of the underserved resi- ptosis, strabismus, and hearing impairment.26 dency track in the Department of Family Medicine at the University of Cincinnati Col- Plain radiographs of the skull are used for lege of Medicine. He graduated from and completed a family medicine residency at the University of Cincinnati College of Medicine. initial evaluation. If craniosynostosis is pre- RICK RICER, M.D., is professor and vice-chair for educational affairs in the Department sent, a three-dimensional CT scan is obtained of Family Medicine at the University of Cincinnati College of Medicine. He received his to detect any underlying brain abnormalities medical degree from Ohio State University College of Medicine, Columbus, and com- and to assist planning for surgery.27 pleted a family medicine residency at DeWitt Army Hospital in Ft. Belvoir, Va. Abnormal brain development that results Address correspondence to Joseph Kiesler, M.D., University of Cincinnati, Department of Family Medicine, 2446 Kipling Ave., Cincinnati, OH 45239 (e-mail: kieslehj@ in microcephaly also can cause a small ante- fammed.uc.edu). Reprints are not available from the authors. rior fontanel or early fontanel closure. Prena-

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tal trauma to the brain, such as maternal alco- seizures, decreased hematocrit, vomiting, and hol abuse, and postnatal trauma, such as hy- alterations in consciousness.20 poxia, are potential causes of microcephaly.20 Tumors also should be considered in the dif- Table 2 20,28 lists the differential diagnosis for ferential diagnosis of a bulging fontanel. Der- microcephaly. moid tumors of the scalp are the most frequent lesions presenting over the anterior fontanel BULGING OR SUNKEN FONTANELS and also may be found over the posterior Disorders associated with increased intra- fontanel.29,30 They usually are slow-growing cranial pressure can cause a bulging anterior and nontender, and they are twice as common fontanel. The most common disorders are among girls. A CT scan is necessary to exclude meningitis, encephalitis, hydrocephalus, intracranial involvement.30 Brain tumors, hypoxic-ischemic injury, trauma, and intra- which can present with signs of increased cranial hemorrhage.20 Table 3 20 lists the differ- intracranial pressure and focal neurologic ential diagnoses for a bulging fontanel. Palpa- findings, are best diagnosed with MRI.31 tion may reveal a tense fontanel that feels The primary cause of a sunken fontanel similar to bone.23 is dehydration. Other signs include reduced Meningitis and encephalitis also cause tem- perature instability, poor feeding, and irri- tability. If meningitis is suspected, a lumbar TABLE 3 puncture should be performed to evaluate the Differential Diagnosis of a Bulging Fontanel cerebrospinal fluid for Gram stain, protein, glucose, cell count, and culture. A CT scan of Hydrocephalus Hematologic disorders a child with meningitis shows the subarach- Space-occupying lesions Polycythemia noid space expanding into the anterior Brain tumor Anemia fontanel.21 Intracranial hemorrhage Leukemia Metabolic disorders Hydrocephalus can result from an imbal- Brain abscess Infections Diabetic ketoacidosis ance between the production and the absorp- Meningitis Electrolyte disturbance tion of cerebral spinal fluid. This condition Encephalitis Hepatic encephalopathy affects 3 per 1,000 live births. Most cases occur Roseola Uremia before two years of age, while the anterior Shigella Galactosemia fontanel is still open. Physical signs include an Mononucleosis Hypophosphatasia abnormal rate of head growth, frontal bossing Lyme disease Osteoporosis of the forehead, widened sutures, and dilated Mastoiditis Maple syrup urine disease scalp veins. Imaging with ultrasonography, Cerebral malaria Miscellaneous CT, or MRI shows enlarged ventricles in the Cysticercosis Hypervitaminosis A absence of brain atrophy. Because ultrasonic Poliomyelitis Lead encephalopathy Aluminum toxicity waves will not penetrate bone, the anterior Endocrine disorders Hyperthyroidism Brain contusions fontanel must be open if ultrasonography is Hypoparathyroidism Hypoxic-ischemic injury 13,15 used for diagnosis. Pseudohypoparathyroidism Coronal synostosis Hypoxic-ischemic injury results in cyto- Addison’s disease Trauma toxic edema and diffuse brain swelling. Asso- Hypothyroidism Dermoid cyst ciated findings include poor feeding, Cardiovascular disorders decreased muscle tone, respiratory difficulties, Congestive heart failure and alterations in consciousness. Intracranial Dural sinus thrombosis hemorrhage can be intraventricular, paren- chymal, subarachnoid, or subdural. Associ- Information from reference 20. ated findings include decreased muscle tone,

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peripheral perfusion, poor skin turgor, and 13. Machado HR, Martelli N, Assirati JA Jr., Colli BO. 32 Infantile hydrocephalus: brain sonography as an sunken eyes. effective tool for diagnosis and follow-up. Childs Nerv Syst 1991;7:205-10. Final Comment 14. Nard J. Abnormal head size and shape. In: Gart- ner JC, Zitelli BJ, eds. Common and chronic symp- An abnormal fontanel in an infant can indi- toms in pediatrics: a companion to the atlas of cate a serious medical condition. Therefore, it is pediatric physical diagnosis. St. Louis: Mosby, 1997: important to understand the wide variation of 95-109. 15. Barkovich AJ. Pediatric neuroimaging. 3d ed. normal, how to examine the fontanels, and Philadelphia: Lippincott Williams & Wilkins, 2000. which diagnoses to consider when an abnor- 16. Faix RG. Fontanelle size in black and white term mality is found. Consultation with a pediatric newborn infants. J Pediatr 1982;100:304-6. 17. Popich GA, Smith DW. Fontanels: range of normal neurosurgeon should be considered if the diag- size. J Pediatr 1972;80:749-52. nosis or presence of an abnormality is unclear. 18. Kliegman RM. The newborn infant. In: Behrman RE, Kliegman RM, Arvin AM, Nelson WE, eds. Nel- The authors thank Bruce Giffin, Ph.D., Department of son Textbook of pediatrics. 15th ed. Philadelphia: Cell Biology, Neurobiology, and Anatomy at the Uni- Saunders, 1996:433-40. 19. Duc G, Largo RH. Anterior fontanel: size and clo- versity of Cincinnati, for review of the manuscript. sure in term and preterm infants. Pediatrics 1986; 78:904-8. The authors indicate that they do not have any con- 20. Tunnessen WW, Roberts KB. Signs and symptoms flicts of interest. Sources of funding: none reported. in pediatrics. 3d ed. Philadelphia: Lippincott Williams & Wilkins, 1999. REFERENCES 21. Rothman SM, Lee BC. What bulges under a bulging fontanel? Arch Pediatr Adolesc Med 1. Soames R. Skeletal system. In: Gray H, Williams PL, 1998;152:100-1. Bannister LH, eds. Gray’s Anatomy: the anatomical 22. Cotran RS, Kumar V, Robbins SL. Robbins’ Patho- basis of medicine and surgery. 38th ed. New York: logic basis of disease. 4th ed. Philadelphia: Saun- Churchill Livingstone, 1995:425-736. ders, 1989. 2. Webster’s II New Riverside university dictionary. 23. Taeusch HW, Sniderman S. Initial evaluation: his- Boston: Riverside Publishing Co., 1984. tory and physical examination of the newborn. In: 3. Simpson DP. Cassell’s Latin dictionary: Latin-Eng- Taeusch HW, Ballard RA, eds. Avery’s Diseases of lish, English-Latin. New York: Macmillan, 1968. the newborn. 7th ed. Philadelphia: Saunders, 4. Adeyemo AA, Omotade OO. Variation in fon- 1998:334-53. tanelle size with gestational age. Early Hum Dev 24. Barness LA. Manual of pediatric physical diagnosis. 1999;54:207-14. 6th ed. St. Louis: Mosby, 1991. 5. Sadler TW, Langman J. Langman’s Medical embry- 25. Tomashek KM, Nesby S, Scanlon KS, Cogswell ME, ology. 8th ed. Philadelphia: Lippincott Williams & Powell KE, Parashar UD, et al. Nutritional rickets in Wilkins, 2000. Georgia. Pediatrics 2001;107:E45. 6. Dale J, Maurer PK. Abnormal head. In: Ziai M, ed. 26. Sundine MJ. Abnormal head shapes in children: Bedside pediatrics: diagnostic evaluation of the classifications and syndromes. J Ky Med Assoc child. Boston: Little, Brown, 1983. 1999;97:202-7. 7. Liptak GS, Serletti JM. Pediatric approach to cranio- 27. Park TS, Robinson S. Nonsyndromic craniosynosto- synostosis. Pediatr Rev 1998;19:352. sis. In: McLone DG, ed. Pediatric neurosurgery: 8. The skeletal system. In: Moore KL, Persaud TV, eds. surgery of the developing nervous system. 4th ed. The developing human: clinically oriented embryol- Philadelphia: Saunders, 2001:345-62. ogy. 6th ed. Philadelphia: Saunders, 1998:414-21. 28. Bellet P. The diagnostic approach to common 9. Fletcher MA. Physical diagnosis in neonatology. symptoms and signs in infants, children, and ado- Philadelphia: Lippincott-Raven, 1998. lescents. Philadelphia: Lea & Febiger, 1989. 10. Haslam R. Neurologic evaluation. In: Behrman RE, 29. Martinez-Lage JF, Torroba A, Lopez F, Monzonis Kliegman RM, Arvin AM, Nelson WE, eds. Nelson MC, Poza M. Cranial fasciitis of the anterior Textbook of pediatrics. 15th ed. Philadelphia: fontanel. Childs Nerv Syst 1997;13:626-8. Saunders, 1996:1667-77. 30. Ruge JR, Tomita T, Naidich TP, Hahn YS, McLone 11. Green M. Pediatric diagnosis: interpretation of DG. Scalp and calvarial masses of infants and chil- symptoms and signs in children and adolescents. dren. Neurosurgery 1988;22:1037-42. 6th ed. Philadelphia: Saunders, 1998. 31. Hart BL, Benzel EC, Ford CC. Fundamentals of neu- 12. Sundine MJ. Clinical findings and treatment of chil- roimaging. Philadelphia: Saunders, 1997. dren with abnormal head shapes. J Ky Med Assoc 32. Mackenzie A, Shann F, Barnes G. Clinical signs of 1999;97:248-54. dehydration in children. Lancet 1989;2:1529-30.

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