Developmental delay — neurological evaluation

Our approach to developmental delay

When a young child is referred for developmental delay, my first job as a paediatric neurologist is to take the description seriously but never to stop at it. "Delay" is a starting point, not a diagnosis. Before we plan anything, I want to know exactly which domains are affected and to what degree — gross motor, fine motor, language (expressive and receptive), social communication, problem-solving and cognition, adaptive function — because the pattern points to very different underlying questions.

The two questions that matter most early are: is this a delay, or has the child lost skills they once had? And: is there a cause we can act on? Global delay (significant lag in two or more domains under the age of five) has an identifiable medical cause in a substantial proportion of children — modern series put the yield of a structured work-up at around half of cases — and that proportion is rising as genomic testing reaches more families. Some of those causes have specific, time-sensitive treatments. Others change the prognosis and the recurrence-risk conversation for the family, even when treatment is supportive. None of this can be sorted out without an integrated, paediatric-neurology-led evaluation.

At the same time, we do not wait for the work-up to finish before starting the right early intervention. The brain is at its most plastic in the first three years, and every month matters. Our approach is to begin the work-up and the intervention plan in parallel — to identify and treat the cause when there is one, to start physiotherapy, occupational therapy and speech and language therapy at the right intensity, and to coordinate everything under one specialist's eye rather than send the family between separate clinics.

What the in-person evaluation looks like

A first visit starts with a detailed developmental, perinatal and medical history, with parents and — where possible — the previous treating team. From there I work through the picture in five overlapping passes.

The first pass confirms and characterises the delay itself. Alongside the clinical examination we apply standardised developmental and cognitive assessment — Bayley-4 (Bayley Scales of Infant and Toddler Development) for younger children, WISC-R for older children where appropriate, and Vineland-3 for adaptive function. Specific delays (language only, or motor only) are mapped separately from global delay, because the question they raise is different.

The second pass distinguishes delay from regression. A careful history — when did each skill appear, when did it plateau, has anything been lost — together with the examination, separates a slow but progressing developmental trajectory from a loss of skills, which is a red flag for neurodegenerative, epileptic-encephalopathy or treatable metabolic conditions where early action changes the outcome.

The third pass searches for an aetiology. Depending on what the history and examination show, we extend the work-up: targeted neurological examination with attention to subtle motor, dysmorphic and skin signs; brain MRI and, where useful, MRS; EEG with sleep where appropriate; chromosomal microarray, gene panel and whole-exome or whole-genome sequencing as the first-tier genetic tests for unexplained global developmental delay; targeted metabolic testing including for treatable inborn errors of metabolism; hearing and vision testing; and thyroid, lead and other directed investigations where the history makes them relevant.

Where the picture needs another set of eyes, I bring in the colleagues we work with regularly — clinical genetics and metabolism, paediatric gastroenterology and a dietitian where feeding or gut concerns are part of the picture, child and adolescent psychiatry, ophthalmology, audiology, and others as the case requires — for fast, focused consultations. Their findings come back to me, and the plan stays single and integrated.

The fourth pass reviews what therapy your child is already receiving — physiotherapy, occupational therapy, speech and language therapy, sensory integration, special education — and asks honestly whether the intensity, the model and the goals match where this child is now. The fifth pass is the plan itself: an early-intervention plan that starts the same day, alongside any precision-treatment options that the work-up identifies.

When delay is not just delay

Most children referred for developmental delay turn out to have a delay, sometimes catchable, sometimes lifelong but supportable. A smaller — but critically important — group have something else, and recognising them early is part of the duty of an integrated paediatric-neurology evaluation. These red flags push us into a different gear: loss of skills the child once had (regression), seizures or staring spells, deteriorating tone or gait, loss of head control, abnormal eye movements, unexplained vomiting or hypoglycaemia, family history of unexplained developmental loss or early death, dysmorphic features, organomegaly, skin or hair findings, or a sudden change in alertness or behaviour.

When any of these are present, the work-up becomes urgent rather than routine. We move directly to brain MRI (sometimes with MRS), EEG (sleep, prolonged or video where appropriate), expanded metabolic and genetic testing, and — where there is a treatable inborn error of metabolism on the table — immediate trial of replacement, restriction or cofactor therapy before final results are back. Treatable causes such as biotinidase deficiency, cerebral folate deficiency, glucose-transporter-1 deficiency, pyridoxine-dependent epilepsy, and several others are not common, but every one of them is reversible if recognised early — and devastating if missed.

Saying "this is just a delay" is a clinical decision that requires real exclusion of these alternatives, not a default. Our approach is to make that exclusion deliberately and document it, so that families know not only what their child has, but also what has been thoughtfully ruled out.