Neuro-Developmental Delay (NDD)

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What is Neuro-Developmental Delay (NDD)?

An occupational therapist’s perspective on the origin of reading and learning disabilities, and sensory dysintegrative disorders.


My own preference is to avoid the term ‘delay’ in describing sensory integrative disorders. By definition a ‘delay’ suggests that whatever it is we are waiting for will arrive at some point. If a child can be trained through a behavioural problem or show significant improvement from meaningful intervention, then we was no longer claim neurological dysgenesis as cause. If they cannot be trained out of a problem and show little benefit from therapy, then this suggests an underlying neurodevelopmental problem, such as dysintegration or some sensory dygenesis. These conditions will not spontaneously resolve, so there is no ‘delay’ per se, simply a lack of full and complete development. It is common for a child to be ‘neurotypical’, that is, developmentally intact and fully neurologically integrated, but not have sufficient experiences to make use of the capacity. These children have functional concerns, more than developmental, and will generally respond well to therapy. DrB


To understand why children can be essentially intelligent but fail to learn in the way that the majority do, it is necessary to understand that the brain is divided into many distinct areas of specialisation. Each area must be connected to each other, and as a whole, to integrate all stimuli to make sense of our world and to enable us to respond to that world. This is technically called sensory motor integration. In another language it can be called processing and we frequently hear of children who are found to have auditory processing delay or difficulty and/or visual processing difficulty. This simply means that the ears and eyes, the nerve pathways, and the appropriate sensory areas in the brain do not register and interpret the stimuli as quickly, or effectively, as in others. It also means that the corresponding motor, or reactive centre, of the brain does not respond as effectively or quickly. If a child cannot hear distinctly or fast enough what is presented to their ears; if they cannot see quickly and sharply what is presented to their eyes; is it surprising then that they experience difficulties with learning? Equally, if their response time is longer than others then they are still cogitating the problem when the rest of the class has moved on. But why does this happen?

When a baby is developing the brain grows from the bottom up, so that the automatic, unconscious, regions of the brain are the first to function. The brain of a foetus and newborn infant is wired in a way to promote initial survival at a reflex level. A reflex is an unconscious predictable response to a specific event or stimulus, for instance the knee jerk following a tap just below the knee. The stimulus / response, involving a simple sensory / motor loop type of nerve pathway, does not interact with the higher conscious brain and the reaction is always the same. We know that a young baby does not have good co-ordination, good eye control or vision. We know that although all the nerve cells are in place at birth most of the connections between the nerve cells and between the specialist centres are not developed. These connections develop all of our lives and are the very essence of learning. Initially most movement is a reflex response to the infants head position, but as the head becomes more controlled the reflex reaction becomes modified. We know that babies develop in stages, each stage heralding more complex abilities and control as the brain matures and new wiring is laid down. These abilities and controls being a combination of more adult “Postural Reflexes” – generating from the mid brain and overriding many of the lower Primitive Reflex reactions – and willed movement initiated by the higher conscious brain. It is also known that the very movements of our baby days, such as rolling, crawling, are essential for our later development. It is these movements that promote the development from the baby wiring to the more adult wiring of the brain.

Sometimes the change from the baby wiring does not proceed as it should, so that the various specialised centres do not develop as well as they should and cannot then perform their function as well as they should. This condition was called by INPP Neuro-Developmental Delay. Not all of those very early reflexes disappear; for instance the knee jerk reaction should remain all of our lives, as do the reflexes that promote breathing and the heart beat. In fact, none of the developmental Primitive Reflexes truly disappear, they simply become outmoded, or inhibited, by the stronger reactions created by the Postural Reflexes. Very few of us are completely without some primitive reaction to head position, but INPP discovered that when a cluster remain, that is 3 or more, they are counter productive to normal neuro-development and can give rise to any number of physical, intellectual, social and emotional developmental difficulties. Some of these symptoms are listed below:

  • • Reading and Writing Difficulty
  • • Numeracy and Organisational Difficulties
  • • Co-ordination Problems and Clumsiness
  • • Poor Concentration / Distractibility
  • • Visual and Auditory Processing Difficulties
  • • Daytime Poor Bladder Control and / or Bedwetting
  • • Delayed Speech and Language Disorders
  • • Hypersensitivity: both physical and emotional
  • • Impulsiveness
  • • Aggressive Outbursts: verbal and physical
  • • Hyperactivity or Immature Behaviour
  • • Stressed, Withdrawn, and over Tired
  • • Lack of Energy and Poor Motivation (Couch Potato)
  • • Balance Problems
  • • Fear of Fairground Rides
  • • School Phobia
  • • Hearing and sequencing difficulties

All of these signs and symptoms are suggestive of a delay in development. An individual may have them in any number; or, in any combination. Obviously the greater the number the greater the developmental delay and the greater the difficulty for the individual and their family.

Normally as the lower centres within the brain grow their circuits upwards, the natural inhibitors develop within the system to block sensory overload and to modify impulse control. Many of the children with Neuro-Developmental Delay do not have these mechanisms in place, they cannot regulate the flow of incoming messages, frequently becoming bogged down by too much information. Just like those days when your tired, or hung over, and there are too many demands, too much noise, too much information to process, too quickly, and with no hold button, or cut off mechanism. And just like you, on those days, too little ability to control the build up of confusion and frustration. Remember though, these individuals have more than their fair share of confusion and frustration. Poor impulse control also accounting for the inability to not say that thought, not pinch that child, not use that word; not tell granny that home truth.

To summarise: the majority of movement in the baby are automatic responses to head position, generated by a collection of reflexes that come from the brain stem. These reflexes are called Primitive Reflexes, all babies are tested for them at birth, they result in instinctual patterns of movements common to all babies. It is these stereotyped movements that result in the development of the baby and why the baby develops in specific chronological stages. Natural progression resulting in the development of new nerve connections (synapses) up through the brain stem into the midbrain. These connections allowing the Postural Reflexes to manage posture, balance and balance adjustment, eye movement and image stability in a much more controlled way. Failure within the mechanisms of development can result in a cluster of Primitive Reflex reactions remaining which will always undermine automatic control.

Sometimes the same difficulties are described in a more formal way, such as:

  • • ADD – Attention Deficit Disorder
  • • ADHD – Attention Deficit Hyperactive Disorder
  • • Dyslexia – Difficulty with language, applied by some to mean reading, writing and sometimes speech, and by others just to mean a reading difficulty.
  • • Dyspraxia – Difficulty with co-ordination
  • • Dyscalculia – Difficulty with numbers.
  • • Dysgraphia – Difficulty with writing
  • • Dystonia – Difficulty maintaining a balanced muscle tone.
  • • PDD – Pervasive Developmental Disorder (more often used in the USA)
  • • DAMP – Deficits in Attention, Motor control and Perception (more often used in Scandinavia)

The above is also a list of symptoms, but using more cryptic terminology. Just because the terms appear to have a medical reference doesn’t necessarily make them more helpful or more justifiable. As you can readily see dys, as a prefix, simply means difficulty. Many people find having a name for a condition helpful, it means that what they have is known about, they are not alone. However, frequently these terms can have different meanings for different people, which can result in very different perceptions of the difficulty, with very different techniques in treatment. These terms tend to refer to the sign or symptom of greatest difficulty, or that part of the condition perceived as presenting the greatest difficulty by the parent or teacher. Many people with dyslexia demonstrate difficulty with maths, co-ordination, writing, attention and maintenance of muscle tone. So given a different day, or tester, that individual could have been named Dyspraxic, ADD, or any of the others referred to above. More accurately, many could be awarded the entire list, ceasing to be a child with difficulties but a whole collection of conditions.

These names refer to the symptoms and are designed to be descriptive, they do not refer to the underlying cause. Treatment, to be effective, must also address that underlying cause; not simply suppress the symptoms. Whether dyslexic, dyspraxic, or having a difficulty with aural-visual integration, disordered or easily distracted, these are are all symptoms suggestive of a developmental delay arising from poor integration of the various separate areas within the brain.