Bulging fontanelle: Difference between revisions

(Expanded with EM-focused content: meningitis workup, normal vs abnormal assessment, red flags, empiric antibiotic regimens, disposition)
(Add verified PubMed references (PMIDs 12825844, 16291356))
 
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==Background==
==Background==
[[File:Sutures from top.png|thumb|Neonatal suture anatomy.]]
[[File:Sutures from top.png|thumb|Neonatal suture anatomy.]]
*Fontanelles are fibrous, membrane-covered gaps between cranial bones
*Fontanelles are fibrous, membrane-covered gaps between cranial bones<ref>Kiesler J, Ricer R. The abnormal fontanel. Am Fam Physician. 2003 Jun 15;67(12):2547-52. PMID 12825844</ref>
*A newborn has six fontanelles: anterior, posterior, two mastoid, and two sphenoid
*A newborn has six fontanelles: anterior, posterior, two mastoid, and two sphenoid
**Anterior and posterior are the most prominent
**Anterior and posterior are the most prominent
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**The anterior fontanelle usually closes between 7-19 months of age
**The anterior fontanelle usually closes between 7-19 months of age
*A bulging fontanelle represents [[Management of Elevated Intracranial Pressure|increased intracranial pressure]], which may be transient and either benign or malignant
*A bulging fontanelle represents [[Management of Elevated Intracranial Pressure|increased intracranial pressure]], which may be transient and either benign or malignant
*Key EM concern: '''[[meningitis (peds)|meningitis]]''' is the most critical diagnosis to rule out in a febrile infant with a bulging fontanelle
*Key EM concern: [[meningitis (peds)|meningitis]] is the most critical diagnosis to rule out in a febrile infant with a bulging fontanelle<ref>Freedman SB, et al. Transient bulging fontanelle after vaccination: case report and review of the vaccine adverse event reporting system. J Pediatr. 2005 Nov;147(5):640-4. PMID 16291356</ref>
*Meticulous history and physical is essential to guide management
*Meticulous history and physical is essential to guide management


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===Infectious (Most Urgent)===
===Infectious (Most Urgent)===
*'''[[Meningitis (Peds)|Meningitis]]''' — must rule out in febrile infant
*'''[[Meningitis (Peds)|Meningitis]]''' — must rule out in febrile infant
*'''[[Encephalitis]]''' / meningoencephalitis
*[[Encephalitis]] / meningoencephalitis
*'''[[Brain abscess]]'''
*[[Brain abscess]]


===Increased ICP===
===Increased ICP===
*'''[[Hydrocephalus]]''' (congenital or acquired)
*[[Hydrocephalus]] (congenital or acquired)
*'''[[Intracranial Hemorrhage (Main)|Intracranial hemorrhage]]''' (traumatic or non-accidental trauma)
*[[Intracranial Hemorrhage (Main)|Intracranial hemorrhage]] (traumatic or non-accidental trauma)
*'''[[Intracranial mass|Space-occupying lesions]]''' (tumor)
*[[Intracranial mass|Space-occupying lesions]] (tumor)
*'''Dural sinus thrombosis'''
*Dural sinus thrombosis
*'''[[Idiopathic Intracranial Hypertension|Idiopathic intracranial hypertension (pseudotumor cerebri)]]'''
*[[Idiopathic Intracranial Hypertension|Idiopathic intracranial hypertension (pseudotumor cerebri)]]


===Metabolic/Endocrine===
===Metabolic/Endocrine===
*'''[[Diabetic ketoacidosis]]'''
*[[Diabetic ketoacidosis]]
*'''[[Inborn errors of metabolism]]'''
*[[Inborn errors of metabolism]]
*Thyroid disorders (hypothyroidism)
*Thyroid disorders (hypothyroidism)
*Parathyroid disorders (hypoparathyroidism)
*Parathyroid disorders (hypoparathyroidism)
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===Other===
===Other===
*'''[[Leukemia (Peds)|Leukemia]]''' (bone marrow infiltration)
*[[Leukemia (Peds)|Leukemia]] (bone marrow infiltration)
*'''[[Anemia]]''' (severe)
*[[Anemia]] (severe)
*'''[[Lead toxicity|Lead encephalopathy]]'''
*[[Lead toxicity|Lead encephalopathy]]
*'''[[Congestive Heart Failure]]''' (with cerebral venous congestion)
*[[Congestive Heart Failure]] (with cerebral venous congestion)
*[[Roseola infantum]] (benign, self-limited — may cause transient bulging fontanelle)
*[[Roseola infantum]] (benign, self-limited — may cause transient bulging fontanelle)
*Post-[[Vaccination Schedule|vaccination]] (benign, self-limited — rare)
*Post-[[Vaccination Schedule|vaccination]] (benign, self-limited — rare)
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===Standard Approach===
===Standard Approach===
*'''[[Head CT]]''' (non-contrast): evaluate for hemorrhage, hydrocephalus, mass, edema
*[[Head CT]] (non-contrast): evaluate for hemorrhage, hydrocephalus, mass, edema
**Obtain before LP if concern for mass lesion or elevated ICP
**Obtain before LP if concern for mass lesion or elevated ICP
*'''[[LP]]''' (lumbar puncture): if not contraindicated by CT findings
*'''[[LP]]''' (lumbar puncture): if not contraindicated by CT findings
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**Send viral studies if encephalitis suspected
**Send viral studies if encephalitis suspected
**Consider HSV PCR in neonates
**Consider HSV PCR in neonates
*'''[[CBC]]''', [[BMP]], blood cultures
*[[CBC]], [[BMP]], blood cultures
*Blood glucose
*Blood glucose
*Consider metabolic workup if no infectious or structural cause identified
*Consider metabolic workup if no infectious or structural cause identified
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==Management==
==Management==
*Treat underlying pathology
*Treat underlying pathology
*'''Suspected meningitis''': empiric antibiotics should NOT be delayed for imaging or LP
*Suspected meningitis: empiric antibiotics should NOT be delayed for imaging or LP
**<1 month: [[ampicillin]] + [[cefotaxime]] (or [[ceftriaxone]] if >28 days) +/- acyclovir
**<1 month: [[ampicillin]] + [[cefotaxime]] (or [[ceftriaxone]] if >28 days) +/- acyclovir
**1-3 months: [[vancomycin]] + [[ceftriaxone]] (or cefotaxime)
**1-3 months: [[vancomycin]] + [[ceftriaxone]] (or cefotaxime)
**>3 months: [[vancomycin]] + [[ceftriaxone]]
**>3 months: [[vancomycin]] + [[ceftriaxone]]
*'''Elevated ICP''': see [[Management of Elevated Intracranial Pressure]]
*Elevated ICP: see [[Management of Elevated Intracranial Pressure]]
**Head of bed elevation 30 degrees
**Head of bed elevation 30 degrees
**Neurosurgical consultation for hydrocephalus or mass
**Neurosurgical consultation for hydrocephalus or mass
*'''Herpes encephalitis''': IV [[acyclovir]] — start empirically in neonates with any suspicion
*Herpes encephalitis: IV [[acyclovir]] — start empirically in neonates with any suspicion
*'''Intracranial hemorrhage''': neurosurgical consultation, correct coagulopathy
*Intracranial hemorrhage: neurosurgical consultation, correct coagulopathy


==Disposition==
==Disposition==

Latest revision as of 10:44, 22 March 2026

Background

Neonatal suture anatomy.
  • Fontanelles are fibrous, membrane-covered gaps between cranial bones[1]
  • A newborn has six fontanelles: anterior, posterior, two mastoid, and two sphenoid
    • Anterior and posterior are the most prominent
    • The posterior fontanelle usually closes by 1-2 months of age
    • The anterior fontanelle usually closes between 7-19 months of age
  • A bulging fontanelle represents increased intracranial pressure, which may be transient and either benign or malignant
  • Key EM concern: meningitis is the most critical diagnosis to rule out in a febrile infant with a bulging fontanelle[2]
  • Meticulous history and physical is essential to guide management

Clinical Features

Normal Fontanelle

  • Soft, flat, or slightly concave when infant is upright and calm
  • May briefly bulge with crying, coughing, or Valsalva maneuver — this is normal and transient
  • Sunken fontanelle suggests dehydration

Abnormal (Bulging) Fontanelle

  • Tense, convex, non-pulsatile fontanelle when infant is calm and upright
  • May feel firm or "full" to palpation
  • Assess with infant calm and in upright position (crying and supine position can cause false bulging)

Associated Findings

  • Fever + bulging fontanelle → meningitis until proven otherwise
  • Irritability, high-pitched cry, poor feeding, vomiting
  • Lethargy, altered mental status, seizures (late signs)
  • "Sunset" eyes (downward gaze deviation — hydrocephalus)
  • Split sutures, rapidly increasing head circumference (increased ICP, hydrocephalus)
  • Bruising, retinal hemorrhages → consider NAT
  • Papilledema (though difficult to assess in infants)

Red Flags

  • Fever + bulging fontanelle (meningitis — requires LP)
  • Altered mental status or seizures
  • Rapidly enlarging head circumference
  • Signs of non-accidental trauma (bruises, retinal hemorrhages)
  • Focal neurologic deficits
  • Apnea or bradycardia

Differential Diagnosis

Infectious (Most Urgent)

Increased ICP

Metabolic/Endocrine

Other

Benign/Transient

  • Crying, Valsalva, supine positioning (normal variant — resolves when calm and upright)

Evaluation

Assessment

  • Examine fontanelle with infant calm and upright
  • Head circumference and comparison to prior measurements
  • Full neurologic exam (tone, reflexes, mental status)
  • Fundoscopic exam if possible (retinal hemorrhages → NAT)
  • Assess vital signs including temperature

Standard Approach

  • Head CT (non-contrast): evaluate for hemorrhage, hydrocephalus, mass, edema
    • Obtain before LP if concern for mass lesion or elevated ICP
  • LP (lumbar puncture): if not contraindicated by CT findings
    • Opening pressure, CSF cell count, glucose, protein, Gram stain, culture
    • Send viral studies if encephalitis suspected
    • Consider HSV PCR in neonates
  • CBC, BMP, blood cultures
  • Blood glucose
  • Consider metabolic workup if no infectious or structural cause identified

When to Obtain Imaging Before LP

  • Focal neurologic deficits
  • Papilledema
  • Signs of severely elevated ICP (altered mental status, bradycardia, hypertension)
  • History of shunt (shunt malfunction)
  • History of CNS disease or mass

Management

Disposition

Admit

  • All infants with bulging fontanelle + fever (pending LP results and cultures)
  • Suspected meningitis or encephalitis
  • Intracranial hemorrhage or mass
  • New hydrocephalus
  • Non-accidental trauma (also alert child protective services)
  • Altered mental status or seizures

Discharge

  • Discharge is rare — only if clearly benign and transient cause identified (e.g., post-vaccination in well-appearing infant with normal exam)
  • Must have reliable caregivers and immediate return access
  • Return precautions: fever, poor feeding, irritability, vomiting, seizure, lethargy

See Also

References

  1. ↑ Kiesler J, Ricer R. The abnormal fontanel. Am Fam Physician. 2003 Jun 15;67(12):2547-52. PMID 12825844
  2. ↑ Freedman SB, et al. Transient bulging fontanelle after vaccination: case report and review of the vaccine adverse event reporting system. J Pediatr. 2005 Nov;147(5):640-4. PMID 16291356
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