Your Brain on Swallowing: How cognitive deficits impact dysphagia

By George Barnes MS CCC-SLP

With the world’s population rapidly aging we should be paying close attention to cognitive deficits and dysphagia, both of which are becoming more prevalent with the growing geriatric community. The elderly are already at an increased risk of cognitive decline and dysphagia and this is without the myriad of diseases and conditions they are susceptible to that may exacerbate this risk. But why are cognitive deficits and dysphagia wrapped together so tightly if they technically are involved with entirely different anatomical areas? Great question… And the answer is...well...complicated.

TV Dinner or Stir Fry?

It would be nice if the body’s systems were gift wrapped in their own separate boxes for us to open up,  pull out, and pick apart so we can figure out what’s wrong. Wouldn’t it be great if the body was like a tv dinner separated evenly by dividers? You have your meat, your potatoes, and your veggies all ready for clean, divided consumption of information. But the body just doesn’t function like that. It’s more like a mixed batch of stir-fried noodles with a medley of meats and veggies; all intermingling and changing each other’s flavor profiles to create a dish of their own (And, now I’m hungry). The point I’m trying to make is that every bodily function impacts the other. Cognition and swallowing are not immune.

Your Brain on Swallowing

To swallow effectively, the body has to have incredible sensitivity to the bolus in order to use its delicate proprioception to create the right timing and coordination of 50 pairs of muscles. It’s no easy feat. But the body does it seamlessly. Almost every time. Almost, every time. A complex system requires strict directions from its complex command center: The brain. When the brain is impaired it shouldn’t be a surprise that the swallowing mechanism may teeter a bit. What IS surprising is that it doesn’t happen more often (thank goodness). 

Even when aspiration does occur, it often doesn’t result in any negative effects. In fact, one study found that 45% of healthy adults aspirate in their sleep (relevant side fact: that number went up to 70% in those with impaired consciousness) and those who did aspirate, actually slept better (tonight I wish you a well-rested sleep filled with recurrent silent aspiration). So while we have been trained to obsess over aspiration, by itself it’s actually pretty harmless. But while aspiration alone is harmless, aspiration pneumonia (though difficult to diagnose) IS dangerous and has been shown to carry a mortality rate of over 20% in the elderly (don’t retire just yet).  Then what do we need for pneumonia to occur? Certain host factors or specific patient characteristics with aspiration (plot twist: altered cognition is one of those factors). 

Dysphagia and Cognition Sitting in a Tree

The brain is a wonderful thing, isn’t it? 3 lbs of fabulous fatty tissue which has unlimited storage capacity, creates enough electricity to power a light bulb and processes information at a speed of 268 MPH. It is also responsible for completing one of the most complex and high-stakes functions of the human body: swallowing. To describe the complex interplay between the brain and swallow function I’ll take a short section from Jenna and Carol Winchester’s wonderful piece on cognitive dysphagia: “The motor cortex, cerebellum, brainstem, cranial nerves, spinal nerves of the cervical/phrenic nerve plexus, and thoracic nerves affect the neuromuscular junctions of the face, larynx, tongue, pharynx, diaphragm, shoulder, neck, external/internal intercostal muscles, rectus abdominus, internal oblique, external oblique, and transverse abdominus. Coordinating top/down and bottom/up functioning of this system and overall perceptual awareness is central to safe deglutition.” I wasn’t joking when I said it’s complicated. With this complex interplay between neural and swallow function, it shouldn’t be a surprise that when cognitive dysfunction occurs, we are left with some dysphagia.

On top of the physiological changes that occur from cognitive dysfunction, dysphagia may also stem from a change in the higher-level processing needed to eat safely. For example, patients with decreased awareness, reasoning, memory, and problem-solving may find it difficult to follow simple directions for safety, compensatory strategies, and weigh the risks/benefits of clinical decision making. Further, many patients with cognitive deficits require somebody to feed them, which has been shown to be the highest indicator for aspiration pneumonia. 

Find the Cause

There is no reason why most elderly patients shouldn’t be able to live long, healthy lives with their cognitive function intact. Despite what we used to think, new brain cells are born throughout the entire life span and cognitive dysfunction is not normal at any age. So when a patient presents with cognitive dysfunction, there has to be a reason for it. Helping to find that reason and managing it is the most valuable thing we can do as practitioners. 

The tough part is that the cause and type of impaired cognition can vary. Widely. Meds? Neuro? Alcohol/drugs? Anesthesia? Is it acute (i.e. delirium) or chronic (i.e. dementia)? Are we expecting anything to change soon or are we looking at baseline? Asking ourselves these types of questions will help us determine the prognosis for the patient, the right timing for our intervention, and if any other temporary alternative options need to be taken to ensure adequate nutrition and hydration (i.e. IV lines or feeding tubes). Pinpointing the cause and helping the team with management options might be the only thing we can do until cognition improves. But it’s an important thing.

Cognition is the Foundation

Cognition is the foundation for all functional activity. As one of the pulmonologists I work with once said, “impaired cognition throws a wrench in the whole system.” What you get is a car without a driver. You can refuel it, repair all of the broken parts, and wash and wax it, but it still won’t drive. Once we find the cause of the cognitive deficit we can help facilitate a plan to remediate it. Remember, the interdisciplinary team looks to us to assess cognitive function so we are in an excellent position to communicate any changes to them so they know if what they’re doing is (or isn’t) working. We can also ask the right kinds of questions to make sure the team is looking at all options (i.e. medications, delirium, drug abuse, dementia, etc.). While we may still need to keep the patient NPO and provide sideline support vs direct intervention, the value we bring to this decision-making process remains priceless. 

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