Nervous System: Reflexes & Disorders – Study Notes

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Nervous System: Reflexes & Disorders

Overview of Primitive Reflexes

Primitive reflexes are automatic movements directed by the brainstem that are present at birth and typically integrate as the nervous system matures. Their retention beyond the expected age can indicate neurological dysfunction and impact motor and sensory development.

Reflex	Purpose	Age Appears	Age Integrates	Signs of Retention
Moro Reflex	Fight or Flight reaction, sympathetic nervous system response	Birth	2-4 months	Hypersensitivity to sensory systems, poor coordination, hyperactivity, poor stamina, adverse drug reactions, poor immunity
Rooting Reflex	Autonomic response to locate food and breast	Birth	3-4 months	Anterior tongue tie, thumb sucking, oral hypersensitivity, articulation problems, swallowing and chewing deficits
Palmar Grasp Reflex	Autonomic flexion of fingers to grab when palm is stimulated	Birth	3-6 months	Poor manual dexterity, deficits with pencil grip, poor writing skills, tactile/proprioceptive dysfunction
Asymmetric Tonic Neck Reflex (ATNR)	Assists with movement through birth canal and cross pattern movements	Birth	6 months	Decreased hand-eye coordination, poor handwriting, poor visual motor skills, tracking problems
Spinal Galant Reflex	Facilitates movement of hips during birth	Birth	3-9 months	Postural issues, misaligned pelvis, bedwetting, decreased endurance, digestive issues, tension in legs
Tonic Labyrinthine Reflex (TLR)	Postural stability for large muscle groups	In utero	3.5 years	Decreased balance, poor spatial awareness, toe walking, poor posture, motion sickness
Landau Reflex	Postural development	4-5 months	1 year	Poor posture, muscle tone, difficulty with activities requiring upper/lower body coordination
Symmetric Tonic Neck Reflex (STNR)	Foundation for crawling	6-9 months	9-11 months	Poor posture, poor seated posture, ape-like position, poor eating, poor hand-eye coordination

Key Primitive Reflexes Explained

Moro Reflex: An involuntary response to sudden loss of support, causing the infant to spread arms, then retract them. Essential for early survival but should integrate by 4 months.
Rooting Reflex: Touching the cheek causes the infant to turn toward the stimulus, aiding in feeding.
Palmar Grasp Reflex: Stroking the palm elicits finger flexion; important for early grasping.
Asymmetric Tonic Neck Reflex (ATNR): Turning the head to one side causes extension of limbs on that side and flexion on the opposite; helps with birth and early hand-eye coordination.
Spinal Galant Reflex: Stroking along the spine causes hip movement; assists in birth and early mobility.
Tonic Labyrinthine Reflex (TLR): Head position influences muscle tone and posture; integrates as postural control develops.
Landau Reflex: When held in prone, the infant lifts head and legs; supports postural development.
Symmetric Tonic Neck Reflex (STNR): Flexion/extension of the head causes corresponding limb movements; foundational for crawling.

Clinical Significance of Reflex Retention

Retention of primitive reflexes beyond the typical age can result in:

Motor coordination deficits
Poor posture and muscle tone
Learning difficulties (e.g., handwriting, reading)
Behavioral and sensory processing issues
Delayed milestones in physical development

Traumatic Brain Injuries

Traumatic brain injuries (TBIs) are physical injuries to the brain that can result in temporary or permanent neurological deficits. Common types include:

Concussion: Temporary alteration in brain function, often due to impact or sudden movement.
Contusion: Permanent damage to brain tissue, usually from a direct blow.
Subdural or Subarachnoid Hemorrhage: Bleeding in or around the brain, increasing intracranial pressure and risking herniation of the brain stem through the foramen magnum, which can be fatal.
Cerebral Edema: Swelling of the brain associated with trauma, which can further increase pressure and damage neural tissue.

Summary Table: Types of Brain Injury

Type	Description	Potential Consequences
Concussion	Temporary alteration in function	Headache, confusion, memory loss, dizziness
Contusion	Permanent damage	Loss of function, neurological deficits
Hemorrhage	Bleeding in brain spaces	Increased intracranial pressure, herniation, death
Cerebral Edema	Swelling of brain tissue	Further injury, increased pressure, risk of herniation

Key Terms

Primitive Reflex: Automatic, involuntary movement patterns present at birth.
Integration: The process by which a reflex is inhibited as the nervous system matures.
Retention: Persistence of a reflex beyond the typical age of integration.
Traumatic Brain Injury (TBI): Physical injury to the brain causing functional impairment.
Herniation: Displacement of brain tissue due to increased intracranial pressure.

Example: Moro Reflex Retention

A child who retains the Moro reflex past 4 months may exhibit hypersensitivity to sensory stimuli, poor coordination, and difficulty with attention and emotional regulation.

Additional info:

Primitive reflexes are assessed in pediatric neurology to screen for developmental delays.
Early intervention can help integrate retained reflexes and improve motor and cognitive outcomes.