Aspiration occurs whenever food
enters the airway below the true vocal folds. Aspiration can
occur before, during, or after the swallow.
Aspiration before the
before the swallow in the case of a delayed or absent
initiation of the swallow. It may also be the result of poor tongue
control, which allows food to trickle into the pharynx while
the patient is still chewing. Apparently, a "neurological
override" exists which prevents the initiation of the
swallow while one is still chewing (Logemann, 1983, 1989,
1997). TRY IT!
Aspiration during the
during the swallow when the vocal folds fail to adduct or
the larynx fails to elevate. (Remember that this type of
dysphagia is uncommon. Only 5% of dysphagias involve
problems with airway closure).
Aspiration after the
occur after the swallow in several different
The patient may
pocket food in the oral cavity. Later, when he or she
lies down to sleep, the food will fall down into the
Food may get
stuck in the pharyngeal recesses. This happens to
everyone, but someone with a normal system would realize
that the food was there and swallow again. A CVA or TBI
patient may have a sensory impairment and allow the food
to drop into the larynx.
Due to reduced
laryngeal elevation, food may remain on top of the larynx
(Logemann, 1989, 1997).
most common type of dysphagia is delayed or absent initiation
of the pharyngeal stage of the swallow. Eighty percent of CVA patients
who have dysphagia have this type of problem (Logemann,
It is common for
patients with this type of disorder to keep trying to push
the bolus into the pharynx with the tongue. Eventually, they
will succeed. Where the food goes when this happens depends
on three things: the posture of the patient, the consistency
of the food and size of the bolus. Smaller amounts of thick
substances will generally lodge in the pharyngeal recesses
rather than going directly down the airway.
As a patient moves
the tongue and tries to push the bolus into the pharynx, the
movements of the tongue and the hyoid bone look a lot like a
swallow. It will be difficult to tell whether or not the
patient is aspirating. A number of patients aspirate without
coughing. Also, food may be lodging in the pharyngeal
recesses, which will hold several teaspoons of material,
before being aspirated.
Disorders of the
pharyngeal stage of the swallow are the most prevalent type
of dysphagia among the CVA population; over 90% have
pharyngeal stage problems. Reduced tongue driving force or
poor pharyngeal stripping action is an especially common
problem among those who have had CVAs. This causes food
residue to accumulate in the valleculae and may lead to
aspiration after the swallow. Pharyngeal stripping action is
usually the last part of the swallowing process to recover.
No specific site of lesion is associated with this
The majority of
patients who are NPO have pharyngeal stage problems.
Fifty percent of those who have pharyngeal stage problems
also have oral stage problems.
Half of CVA
patients with dysphagia have problems that affect the
stage of the swallow. Fifty percent of those have reduced
or abnormal tongue movements that affect the initiation of
the swallow. Typically, tongue control problems are not
sufficiently severe to cause aspiration. No specific site of
lesion is associated with tongue movement problems.
5% of CVA patients have problems with
vocal fold adduction. This type of difficulty only occurs
with brain stem (cranial nerve x) lesions.
There are generally no problems
with airway closure following a cortical stroke, unless
there are bi-lateral upper motor neuron lesions (pseudo bulbar palsy).
5% of CVA patients have swallowing
problems caused by the failure of the cricopharyngeus
muscle (p.e. segment) to relax. If the p.e.
segment does fail to relax, food will build up in the
pharynx and may be aspirated. In this case food residue will
be accumulated in the pyriform sinuses, or in cases of severe
problems, throughout the lower portion of the pharynx, and
may cause aspiration after the swallow.
*** Typically, each patient will have more than one type of
There is currently
enough evidence to specify the specific type of swallowing
problem associated with particular sites of lesion caused by
stroke typically causes the most severe cases of dysphagia.
Damage to the medulla is particularly devastating as is to
be expected since the "swallowing center" and the nuclei of
most of the cranial nerves involved in swallowing are
located there. As the cranial nerves are lower motor
neurons, they form the final common pathway for all motor
(pyramidal and extrapyramidal tracts) impulses traveling from the brain to the muscles involved in
deglutition and speech (Logemann, 1983, 1997, Reed, 2011).
According to Reed, 2011 "Many people with brainstem strokes cannot eat and drink safely due to the risk of aspiration." Patients with
unilateral medullary lesions may have functional or even
normal oral control. However, they usually have significant
problems with the pharyngeal stage of the swallow (the
cranial nerves that innervate the pharynx and larynx
originate in the medulla). They may have one or more of the
following problems: extreme delay in the initiation of the
swallow response (10-15 seconds) and reduction in both
elevation and anterior movement of the larynx. This in turn
may lead to reduced opening of the criopharyngeus muscle.
They may also have unilateral pharyngeal weakness and
unilateral vocal fold paralysis. In some cases, patients
will not recover their swallow for 4 to 6 months or
stroke can affect both sensory and motor
pathways. It may cause problems in both the oral and
pharyngeal stages of the swallow, including:
• Mild delays in oral transit time (3-5 seconds)
• Mild delays in initiation of the pharyngeal swallow ( 2-3 seconds)
• Impairments in the timing of the neuromuscular components of the pharyngeal swallow. (Logemann, 1989)g
following problems may be experienced:
Mild oral transit
delays (2-3 seconds)
pharyngeal delays (3-5 seconds)
produced by right hemisphere lesions while anatomically and physiologically no more
severe than those resulting from left hemisphere
damage have poorer outcomes. Patients with right hemisphere damage tend to
have attentional problems and exhibit poor judgment
including impulsivity. These characteristics reduce
their ability to use compensatory strategies for safe
Strokes often cause significant swallowing
problems that affect both the oral and the pharyngeal
stages. Also, cognitive ability may be impaired, reducing
the patient's ability to use compensatory strategies.
According to Logemann (1989), the swallow is never quite the
same after a stroke even when a patient is able to return to
a regular diet. When a patient has another stroke later, the
already compromised mechanism is further damaged.
In recovery of the
tongue movement is generally the first part of the process
to improve, followed by the initiation of the swallow.
Pharyngeal stripping action is usually the last part of the
process to improve in recovery.
Recovery is most rapid in the first 3
or 4 weeks after a stroke. Therefore, an SLP should always
re-evaluate an NPO patient about one month after a
Generally, if the
swallow is going to recover it will do so within 6 or 7
weeks after a stroke.