Neurological examination of the neonate

Despite the use of advanced neurophysiological and neuroimaging techniques, there remains no substitute for the clinical neurological examination.

The purpose of the neonatal neurological examination is to:
1) Diagnose neurological abnormality
2) Assess progression of encephalopathy
3) Provide prognostic information on long term neurological injury

 

Physiological background: what is the neurological examination telling us?

The neurological examination should allow the physician to identify whether the patient is neurologically normal, and if abnormal, to hypothesise where within the nervous system the problem may lie.

The neurological examination is grouped into 5 subdivisions – each focusing on the function of a different level of the nervous system:
i) Behavioural observation assess global brain function through evaluation of the infants alertness, response to the environment and orientation to sensory stimuli.
ii) Cranial nerve testing is similar to older children, and reflects brainstem and cranial nerve function.
iii) Assessment of posture, tone, deep tendon reflexes and strength are used to evaluate the motor system.
iv) Sensory examination of the newborn is difficult – although a graded response to graded stimulation in the trunk and extremities remains useful.
v) Observation of generalized movements and evaluation of primitive reflexes assess overall coordination.

In contrast to children or adults, which commonly present with focal findings, abnormalities in the neonatal neurological examination are often global and non-specific. Importantly the neurological examination of an infant with brain injury evolves over time. Non-specific encephalopathy and/or hypotonia in the acute period is often followed by a period of improved alertness and pseudonormalisation of tone subacutely before proceeding on to the development of chronic spasticity with or without cognitive impairment. Therefore any baby who presents with abnormal neurology in the neonatal period should have careful long-term assessment as ‘normalisation’ in the first days/weeks of life can be falsely reassuring.

 

How is the neonatal neurological examination performed and interpreted.

Pioneers in the field of neonatal neurological examination were Saint-Anne Dargassies and Amiel-Tison in the 1960’s. While their approach focused on tone and reflexes, other methods addressed different aspects of the neurological system: the Prechtl Method focuses on generalized movements, the Brazelton Scale incorporates behavioural assessement. Probably the most commonly used assessment is the Dubowitz method; this method is designed to be performed at the cotside by paediatricians or neonatologists with little or no formal training. The examination consists of 34 items organized into six groups: tone, tone patterns, reflexes, movements, abnormal signs and behaviours.

These items are illustrated on a proforma, which provides both instruction for each item and allows the examiner to circle the response that most closely matches their observation. The proforma indicates the ‘optimal’ finding for a given gestational age and also indicates which findings are outside the 5th or 10th centile (suboptimal). For each infant an ‘optimality’ score can be calculated. Studies on healthy term infants have shown that abnormalities of 1-2 single exam items should not raise undue concern. However an examination that reveals multiple suboptimal responses is uncommon and is grounds for further evaluation. Using this proforma, interrater reliability has been shown to be above 96% even among inexperienced users. The sensitivity and specificity of the examination has been shown to be 91% and 79% respectively: ie using a cut off of 2+ abnormal signs, 91% of children with abnormal signs were identified by the examination and 79% of infants with an abnormal examination went on to have abnormal neurology.

The Dubowitz screening tool consists of 12 items from the full examination proforma. Two or more abnormal findings are considered ‘warning signs’, warranting full neurological examination. A normal full Dubowitz examination – or one with 1-2 abnormal single exam items – will rule out 1 year neurological outcome for an individual child with very good accuracy. Multiple abnormal findings on examination indicate a need for further evaluation for neurological abnormality – but is not in itself diagnostic.

 

Examination of the preterm infant at term

The Dubowitz examination has been further evaluated in preterm infants, with normative reference data for preterm infants who were born at varying gestational age and examined at term equivalent age. Unlike term infants, healthy preterm infants at term have a broader range of responses on each item, which varied depending on the infants’ gestational age at birth. Low-risk preterm infants tend to have lower flexor tone in limbs, more hyperexcitability and less smooth, fluid movements as compared with term infants. Like the healthy term infant, an isolated abnormality in a single examination is not uncommon, more than 4 abnormal findings should warrant further evaluation.

In preterm infants with known cerebral lesions on cranial ultrasound an increased number of abnormal single exam items predicts abnormal neurology at 2 years of age: a median score different in six items predicted normal neurology; a median score different in 12-18 predicted hemiplegia or diplegia and a median score >24 predicted tetraplegia.

 

The Dubowitz Neonatal Neurological Examination

Please click here for the Hammersmith Neonatal Neurological Examination guide. Adapted from: Hammersmith Neonatal Neurological Examination in Dubowitz L, Dubowitz V, Mercuri E. The neurological assessment of the preterm and full term newborn infant. Clinics in Developmental Medicine. 1999

 

Adapted from an article: Wusthoff CJ. How to use: the neonatal neurological examination. Arch Dis Child Educ Pract Ed 2013;98:148-153.