Necessity of Intracranial Imaging in Infants and Children With Macrocephaly

Macrocephaly is a common condition defined as head circumference greater than the 97th percentile or 2 standard deviations above average for their age.¹ It is a frequently encountered by pediatricians, pediatric neurologists and pediatric neurosurgeons. Differential diagnosis for macrocephaly is broad, ranging for benign familial macrocephaly to rare metabolic disorders.¹ Children presenting with this condition often get head imaging as there are no standardized guidelines to determine the need for imaging. Most of them do not have any pathologic intracranial abnormalities. Types of head imaging include head ultrasound (HUS), head CT, and brain MRI, which each have either limitations or potential complications associated with them. HUS can be performed only in children with a patent anterior fontanelle and may be difficult to use in older children.¹ CT head is associated with radiation exposure and secondary oncologic sequelae.^2-5 MRI brain typically requires sedation in younger children which can be associated with complications.^2-5 Therefore, it is important to analyze the need for imaging to avoid unnecessary testing.

This retrospective chart review was performed to assess the risk factors for abnormal imaging in children with macrocephaly and to formulate an algorithm that can guide physicians. Inclusion criteria included age less than 36 months of age, a diagnosis of macrocephaly, and neuroimaging. Exclusion criteria included a reason for neuroimaging other than macrocephaly (e.g seizures, headache, and trauma) evaluation were excluded. 169 patients were identified with a total of 183 imaging studies, approximately half of which were HUS. Neuroimaging results were classified as normal, benign external hydrocephalus (BEH), or abnormal. Abnormal studies were dichotomized as either low yield findings (such as periventricular leukomalacia, which did not necessitate such interventions and were not thought to have a causal relationship with macrocephaly), or high yield findings (those requiring further follow-up or action such as surgical intervention, specialist referral, or hospitalization).

The vast majority of patients had studies that were either normal (58.6%) or demonstrated BEH (33.7%). Only 13 patients’ studies were abnormal (7.7%), 5 (2.9%) of which were classified as high yield. These included two with marked hydrocephalus requiring ventriculoperitoneal shunt placement, two with chronic subdural hemorrhage concerning for nonaccidental trauma, and one demonstrating a Chiari 1 malformation and hydrocephalus. Three of the 5 patients with high yield abnormalities carried a diagnosis of developmental delay, two of whom also had an abnormal neurological exam. 64.4% of the 59 patients with documented family history had a family history positive for macrocephaly, none of whom had abnormal findings on neuroimaging.

Statistical analyses supported both developmental delay (P = 0.04) and an abnormal neurological exam (P = 0.015) as significant risk factors for high yield imaging abnormalities. Based on these factors the authors formulated a simple algorithm to determine the need for neuroimaging in patients with macrocephaly.

This study has a few limitations, one of which was small sample size. Another was its retrospective nature, as chart analysis can be limited by insufficient documentation by primary physician. A third limitation of the study was that the ages at which HUS were obtained were not been specified. HUS was the dominant type of imaging used in this patient population probably because it is cheaper and more easily available than other types of imaging.^4,5 However, HUS may have limitations, particularly in children 6 months or older, as closing sutures may limit the sensitivity.¹ The preponderance of HUS may have also been a limitation. Haws et al. showed demonstrated that MRI may demonstrate abnormalities missed by HUS in patients with macrocephaly.⁴ The authors of the current study mentioned the potential benefit of using quick brain MRI, which usually does not require sedation and is cheaper than a complete MRI. The study did not address the appropriate frequency and duration of subspecialty clinic follow up for patients being observed without imaging, as these patients are often seen by neurology or neurosurgery. Overall this study provides good direction in management of macrocephaly and shows the need for future prospective studies.

References

[1]Orrù E, Calloni SF, Tekes A, Huisman TAGM, Soares B. The child with macrocephaly: Differential diagnosis and neuroimaging findings. AJR American Journal of Roentgenology 2018;210:848–59. doi:10.2214/AJR.17.18693.

[2]Malviya S, Voepel-Lewis T, Eldevik OP, Rockwell DT, Wong JH, Tait AR. Sedation and general anaesthesia in children undergoing MRI and CT: adverse events and outcomes. Br J Anaesth 2000;84:743–8. doi:10.1093/oxfordjournals.bja.a013586.

[3]Roback MG, Wathen JE, Bajaj L, Bothner JP. Adverse events associated with procedural sedation and analgesia in a pediatric emergency department: a comparison of common parenteral drugs. Acad Emerg Med 2005;12:508–13. doi:10.1197/j.aem.2004.12.009.