What causes loss of sucking reflex?

Causes of Loss of Sucking Reflex

The sucking reflex is a critical primitive reflex that can be lost due to various neurological and developmental conditions. Loss of the sucking reflex is primarily caused by stroke, neurodegenerative diseases (such as Parkinson's disease and dementia), and damage to dopaminergic neurons in the central nervous system. 1

Neurological Causes

• Stroke is one of the most common conditions leading to oropharyngeal dysphagia and loss of sucking reflex, with aspiration observed in over one-third of acute stroke patients 1
• Progressive neurologic diseases including dementia, amyotrophic lateral sclerosis (ALS), and Parkinson's disease frequently cause deterioration of the sucking reflex 1
• Loss of dopaminergic neurons in the central nervous system due to stroke or neurodegenerative diseases directly contributes to decreased swallow reflex function 1
• Delayed maturation of the sucking-swallowing reflex can occur in infants, presenting with difficulty in sucking or swallowing despite normal development 2

Anatomical and Structural Causes

• Cervical spine surgery can lead to aspiration and swallowing dysfunction in over 40% of patients 1
• Head and neck cancer and related treatments (tumor resection) can disrupt the normal swallowing mechanism 1
• Endotracheal intubation can result in temporary or permanent damage to structures involved in the swallowing process 1
• Sarcopenia (decreased muscle mass and quality with advancing age) affects the muscles used for swallowing, contributing to loss of sucking and swallowing function 1

Age-Related Factors

• Normal aging leads to alterations in olfaction and gustatory sensation that affect the entire swallowing process 1
• Force generation capacity of the oral tongue decreases with advancing age, leading to reduced pressure generation during the oral phase and poor bolus clearance 1
• Changes in the muscles of mastication result in slower and inefficient chewing in older adults 1
• Lower salivary flow rates associated with aging can contribute to xerostomia and swallowing difficulties 1

Medication-Related Causes

• Anticholinergic medications can directly impair swallowing function and contribute to loss of sucking reflex 1
• Certain medications contribute to decreased appetite, incoordination, and esophagitis, exacerbating swallowing problems 1
• Acetylcholinesterase inhibitors used for symptomatic treatment of Alzheimer's disease can paradoxically affect oral motor function 3

Developmental Considerations

• In infants, the sucking reflex is normally present at birth but may be absent or impaired in neurologically affected infants 4
• The normal developmental transition from primitive sucking reflex to mature swallowing occurs as the pharynx lengthens and enlarges, the larynx lowers, and the mandible and hyoid descend 1
• Children typically achieve an adult pattern of muscle activation during oral and pharyngeal phases of swallowing by ages 5 to 8 years 1

Clinical Implications and Assessment

• Prior to considering pharmacological treatment for a patient with loss of sucking reflex or oropharyngeal dysphagia (OD), a clinical swallow exam or instrumental swallow evaluation should be performed 1
• Pharmacological treatment options, particularly TRPV1 agonists (capsaicinoids and piperine) and dopaminergic agents, may help patients with delayed swallow reflex 1
• Application of levodopa has been shown to normalize the onset of pharyngeal swallow in patients with post-stroke oropharyngeal dysphagia 1
• Subjective reports by patients or caregivers of coughing while eating and drinking can help identify those at risk for aspiration due to loss of swallowing reflexes 1

Therapeutic Approaches

• Oral motor therapy has shown beneficial effects on feeding problems in children with cerebral palsy who have impaired sucking reflexes 5
• Functional Chewing Training can improve chewing performance and reduce tongue thrust severity in children with cerebral palsy 6
• For infants with neurological impairment affecting sucking, various techniques of stimulation, positioning, and progressive weaning can help establish feeding 4
• Multidisciplinary team treatment, including early evaluation by a speech-language pathologist, is associated with improved outcomes in patients with dysphagia 1

Pitfalls and Caveats

• Silent aspiration (aspiration without cough response) is common in patients with impaired sucking and swallowing reflexes, making clinical detection challenging 1
• Apparent hypersalivation may be due to pooling from impaired clearance rather than overproduction, particularly in patients with neurological disorders 3
• Due to limited evidence regarding clinical endpoints, pharmacological treatment decisions for swallowing disorders need to be based on careful risk-benefit analysis 1
• When evaluating swallowing function in older adults, it's important to distinguish whether dysphagia is a significant contributor or if other factors predominate 1