Incidental Findings on Brain MRI for Pediatric Headache

Magnetic resonance imaging (MRI) scans of the brain are commonly performed in patients with primary headache, particularly migraine.These scans have been found to reveal incidental findings and anatomical variants that are not likely the cause of headache in up to 31% of adults and 21% of children in the United States.^1,2 While such findings are rarely associated with serious underlying pathology in pediatric neurology patients (0.3% to 3.4%), they “may lead to anxiety and concern for patients and parents,” Randolph W. Evans, MD, clinical professor of neurology at Baylor College of Medicine, told Clinical Pain Advisor.³

According to practice guidelines for the evaluation of children with recurrent headaches, neuroimaging should be considered in children with abnormal neurologic findings on examination or physical findings that may indicate central nervous system disease.⁴ In patients with a normal neurologic examination, routine neuroimaging is not indicated, and “close clinical follow-up without imaging is the most cost-effective strategy,” Dr Evans and colleagues wrote in a recent review published in Headache.⁵ “Children with non-migrainous headache episodes lasting more than 6 months and a normal neurologic exam have a low baseline risk for brain tumor of 0.01%,” they wrote.

Rare incidental findings include brain tumors, focal cortical dysplasia, Rathke’s cleft cysts, colloid cysts, gray matter heterotopias, periventricular leukomalacia, and physiologic pituitary hypertrophy, said Dr Evans. Some of the more common incidental findings are summarized below.

• Nonspecific white matter abnormalities (WMA). Found in 4% to 5% of pediatric MRIs, nonspecific WMA are seen on T2-weighted sequences as small hyperintense foci.⁶ Studies indicate an association between migraine and deep white matter hyperintensities in women only. In patients with migraine, the typical location of WMA is supratentorial and there is no elevated risk for lesions of the brainstem or cerebellum. “In contrast, [in] multiple sclerosis (MS) lesions, there is preferential involvement of the subcortical U-fibers, the corpus callosum, temporal lobes, and the brainstem/cerebellum,” note the article’s authors. “MS periventricular lesions are ovoid and perpendicular to lateral ventricles.” In patients who are asymptomatic but show signs of MS on MRI (known as “radiologically isolated syndrome”), follow-up imaging should be performed on a case-by-case basis.
• Venous angiomas. Also known as developmental venous anomalies (DVAs), venous angiomas have been observed in 0.3% to 2.1% of pediatric patients. These are “congenital anomalies of interacranial venous drainage characterized by the ‘caput medusae sign’ of veins draining into a single larger collecting vein, which in turn drains into either a dural sinus or into a deep ependymal vein,” as described in the review. In 75% of DVA cases, the lesion is isolated. As many as 33% of patients with DVAs have an associated cavernous hemangioma, which may confer a higher risk for hemorrhage. In these cases, referral for neurosurgical consultation is indicated.⁷

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• Arachnoid cysts are observed in 1.3% to 2.0% of children imaged. While headache is the most common symptom, the cyst is frequently incidental. Referral for neurosurgical consultation is indicated if cysts are accompanied by focal neurological findings or signs of intracranial pressure.
• Pineal cysts are found on pediatric MRI in an estimated 0.8% to 2.1% of cases. Headaches in patients with pineal cysts are usually coincidental. Large cysts can cause gaze palsy or Parinaud syndrome. If the maximal cyst dimension is >1 cm, referral for potential neurosurgery is indicated. In asymptomatic children, follow-up MRI should be performed 1 year later.
• Enlarged Virchow-Robin spaces (VRS). VRS are “normally sized perivascular spaces of interstitial fluid that surround intracranial blood vessels that can be appreciated on 1.5 Tesla MRI,” the researchers explained. They are most often located in the basal ganglia, vertex, anterior commissure, and midbrain. While enlarged VRS (<5 mm) can be a normal consequence of age-related brain atrophy, severely enlarged VRS can be an early consequence of mild traumatic brain injury or metabolic/genetic, vascular, inflammatory, or neoplastic abnormalities. Although more commonly noted in migraineurs, most patients with enlarged VRS are asymptomatic.
• Mega cisterna magna. Observed as an incidental finding in 0.4% of pediatric patients and 10 mm or larger on midsagittal view, mega cisterna magna is an “enlarged subarachnoid space in the inferior and posterior portions of the posterior fossa with [a] normal appearing cerebellar hemispheres, vermis, and fourth ventricle” the investigators stated. While it is considered benign and does not require intervention or follow-up imaging, clinicians should conduct a careful evaluation to differentiate a suspected mega cisterna magna from an arachnoid or epidermoid cyst, Blake pouch cyst, congenital cerebellar hypoplasia, Dandy-Walker malformation, cerebellar atrophy, or tumors such as pilocytic astrocytoma.

Dr Evans suggests that clinicians preemptively address parents’ concerns prior to performing MRI. “Given how often incidental findings are present, it is often useful to discuss the possibility of incidental findings before the scan is done to allay future anxiety,” he said.

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References

1. Kim BS, Illes J, Kaplan RT, Reiss A, Atlas SW. Incidental findings on pediatric MR images of the brain. AJNR Am J Neuroradiol. 2002; 23(10):1674-1677.
2. Evans RW. Incidental findings and normal anatomical variants on MRI of the brain in adults for primary headaches. Headache. 2017; 57(5):780-791.
3. Gupta SN, Gupta VS, White AC. Spectrum of intracranial incidental findings on pediatric brain magnetic resonance imaging: What clinician should know? World J Clin Pediatr. 2016; 5(3):262-272. 
4. Lewis DW, Ashwal S, Dahl G, et al; Quality Standards Subcommittee of the American Academy of Neurology; Practice Committee of the Child Neurology Society. Practice parameter: evaluation of children and adolescents with recurrent headaches: report of the Quality Standards Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society. Neurology. 2002; 59(4):490-498.
5. Strauss LD, Cavanaugh BA, Yun ES, Evans RW. Incidental findings and normal anatomical variants on brain MRI in children for primary headaches. Headache. 2017; 57(10):1601-1609.
6. Bayram E, Topcu Y, Karaoglu P, Yis U, Guleryuz HC, Kurul SH. Incidental white matter lesions in children presenting with headache. Headache. 2013; 53(6):970-976.
7. Buhl R, Hempelmann RG, Stark AM, Mehdorn HM. Therapeutical considerations in patients with intracranial venous angiomas. Eur J Neurol. 2002; 9(2):165-169.