Neurological examination across childhood — branching viva

Opening framework

My framework has three layers. First, the constant structure — the same six-part neurological examination at every age: mental state, cranial nerves, motor, sensory, cerebellar and gait, and development. Second, the developmental reading — every finding is read against what is normal for the age, because the corticospinal tracts myelinate through infancy and the meaning of a sign changes with the maturity of the central nervous system. Third, the standardised infant tools — the General Movements Assessment and the Hammersmith Infant Neurological Examination — which detect cerebral palsy months before a classic motor examination can. [1]

The four-month-old with right-sided hypertonia and absent fidgety movements

An extensor plantar response and a few beats of unsustained ankle clonus are normal in a young infant because the corticospinal tracts are incompletely myelinated at birth, and the inhibitory pathway that flexes the toe matures over the first twelve to twenty-four months. Here the finding is asymmetric — extensor on the right only, with right-sided hypertonia and brisk right-sided reflexes — so it is pathological in context. The tone is increased on the right with a velocity-dependent catch on fast stretch, which is spasticity by the Task Force on Childhood Motor Disorders definition, distinguishing it from dystonia (co-contraction with movement) and rigidity (continuous, velocity-independent resistance). [2] [6]

Absent fidgety movements at corrected age nine to twenty weeks post-term are among the strongest single predictors of cerebral palsy. The normal fidgety repertoire is continuous, variable, low-amplitude movements of the neck, trunk and limbs; its absence, combined with a low Hammersmith Infant Neurological Examination score and an abnormal magnetic resonance imaging, allows an early, accurate diagnosis before corrected age six months. The integrated pathway — General Movements Assessment plus Hammersmith plus magnetic resonance imaging — replaced the older watch-and-wait approach, and international guidelines now endorse early intervention from that window. [4] [8]

Branch: the floppy, alert infant with areflexia and tongue fasciculations

For the floppy three-month-old with areflexia, tongue fasciculations and preserved social engagement, the hypotonia is peripheral. The reflexes are absent in proportion to the weakness, yet the infant is alert and socially engaged, which excludes a primary central cause — a central cause would preserve or increase the reflexes and typically reduce the social engagement. The most likely diagnosis is spinal muscular atrophy, supported by the severe symmetric proximal weakness, the areflexia, and the tongue fasciculations. [10]

The progressive reduction in movement raises the urgency because spinal muscular atrophy is a progressive lower motor unit disorder that can compromise the respiratory muscles over weeks to months, and because disease-modifying therapy is now available and time-critical. The investigations are genetic testing for the survival motor neuron gene and electromyography with nerve conduction studies to confirm the anterior horn cell localisation. The contrast is the central floppy infant — reduced tone but preserved or brisk reflexes, persistent primitive reflexes, and reduced social engagement — whose cause lies in the brain, as in hypoxic-ischaemic injury or a chromosomal syndrome. [12]

Closing: assigning a Gross Motor Function Classification System level

For the same child at age four with confirmed cerebral palsy, I complete the examination by assigning a Gross Motor Function Classification System level, the five-level ordinal scale that describes the child's usual gross motor ability and predicts the motor trajectory. Level one is a child who walks without limitation; level two walks with limitations; level three walks with a handheld mobility device; level four has self-mobility with limitations and may use powered mobility; and level five is transported in a wheelchair with severe limitation of even basic voluntary movement. The level, once stable, anchors the prognosis, the rehabilitation goals, and the equipment plan, and it is re-stated at intervals as the child grows. [7]

The longer lesson is the trajectory and the disposition. Every child leaves the examination with a documented finding, a clear plan, and a written safety-net — the head crossing centiles, the loss of a skill, the focal deficit, or the change in conscious state are the features that return urgently. The examination is not a single event but a developmental act, performed and re-read at every contact, and the candidate who holds the developmental clock alongside the constant framework has mastered the discipline. [9]