Neuroimaging to diagnose central nervous system tumours in children

Delay in diagnosis

The process leading to diagnosis of CNS tumours usually starts with parents noticing symptoms and seeking medical advice from a primary care physician. Thereafter, the physician may raise the alert if there is concerning medical history or a noticeable deficit upon neurologic physical examination, resulting in referral to a specialist. Following this, imaging is usually undertaken to support a definitive diagnosis of CNS tumour. Shortening these prediagnostic symptomatic intervals ([PSIs] 1, 2, and 3, respectively) is critical to shortening time to diagnosis and treatment.

Factors associated with delay in diagnosis have been documented in the literature and include older age (usually older than 4 years), benign tumours (owing to their slow progression), and location of tumours in the supratentorial region (low-grade glioma, for example).

While diagnostic delay may not impact cure rates,⁴ it is likely to affect morbidity⁵ and to increase the stress on families.⁶

Tumour symptoms in CNS

Symptoms of CNS tumours are similar to those of other common conditions and include headache, vomiting, lethargy, and seizures, and there are no pathognomonic features, making the diagnosis in children difficult.³ In a review of 163 children in British Columbia with CNS tumours between 2000 and 2016, the most common symptoms were headache, vomiting, seizures, and ataxia. Forty percent of children presented with hydrocephalus and 17.6% presented with clinically detectable papilledema.⁷ Other symptoms that have often been associated with delay in diagnosis include vision changes, weakness, pain, behavioural symptoms, and endocrinopathies.^8,9 A single sign or symptom, unless it is a prominent focal abnormality on neurologic examination, is uncommon at the time of diagnosis.¹⁰ Psychological changes have also been noted to be frequent among children with CNS tumours. Some physical symptoms may be considered to be psychosomatic in origin.¹¹

However, most children with a CNS tumour will have notable signs on a full physical examination.³ In an analysis of 3276 pediatric patients, less than 3% of those with headache and a brain tumour had no findings of abnormality on careful neurologic examination,¹² and among 72 children with CNS tumours whose symptoms started as headache, abnormalities on physical examination had developed in 85% within 2 months of headache onset.¹³ Thus, a comprehensive physical examination, including ophthalmoscopy, would help care providers identify those children who require prompt imaging studies.³

When to image

In recent years, Canada has seen better access to advanced imaging, including computed tomography (CT) and magnetic resonance imaging (MRI). However, risks from exposure to radiation from CT and the need for sedation in young children for MRI, with its own inherent risks, necessitates judicious use of each of those tests. The imaging chosen as the first step will likely depend on patient- and health system–related factors. Obtaining a CT scan of the brain as the first step may be faster in most centres in Canada.

The United Kingdom’s National Collaborating Centre for Primary Care developed referral guidelines for suspected cancer, including specific guidance for children and young people.¹⁴ Based on its systematic review of the literature and Delphi consensus process,¹⁵ it concluded that MRI is the modality of choice for making a diagnosis, when possible, and recommended that patients selected for nonemergency imaging have that imaging performed within 2 weeks of presentation, with results given to the family within 1 week afterward.

Preventing delays

After finding considerable delays in CNS tumour diagnosis in a national survey in the United Kingdom,⁸ the Royal College of Paediatrics and Child Health launched the HeadSmart initiative in 2011^16,17—a practitioner-targeted awareness quality improvement strategy, followed by a public awareness campaign. This initiative used a systematic review and meta-analysis to identify age-related differences in symptoms. Awareness materials with an age-stratified symptom checklist and algorithms for urgent referrals were distributed to health care professionals, health organizations, professional bodies, and the public (schools, child care facilities, hospital waiting rooms, local authorities, charities, and commercial networks). The result was a meaningful decrease in median PSI from 14 to 6.7 weeks.¹⁸ The authors recommend obtaining brain imaging within 4 weeks if a child presents with symptoms and signs that may be due to a CNS tumour. We advocate applying the same criteria in Canada in order to reduce PSI.

In a survey of practising Canadian family physicians,¹⁹ participants described barriers to diagnosis in Canada, including long wait times for consultation and imaging investigations, the geography of Canada (distance to tertiary care centres), access to resources (specialist information and current guidelines on investigations and management), lack of experience given the rarity of diagnosis, patient-related factors (young age, need for sedation), and health system barriers. More than 80% of those surveyed were not aware of any available resources or guidelines to help manage a patient or navigate a referral, and dissemination of an online resource like HeadSmart may provide helpful general educational materials for both care providers and patients.