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A) Burns (thermal, caustic, laser)
Thermal, electrical, and laser
energy and corrosive chemicals can cause circumferential stenosis of the oral
cavity, pharynx, larynx and esophagus (44) (113). These stricture-causing injuries
are usually severe, impairing alimentation, breathing, airway protection and phonation
(45) (114).
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B)
Cervical spine surgery
Dysphagia is a recognized potential complication
of anterior cervical spine surgery and it is usually transient, resolving within
a few weeks, but it may be protracted or even permanent and require more extensive
diagnostic and therapeutic intervention (46, 47, 48) (115-117). Studies utilizing
videofluoroscopic swallow study, laryngeal videostroboscopy and EMG of patients
with new-onset dysphagia after anterior approach to the cervical spine reveal
a number of possible contributing factors: prevertebral soft tissue swelling at
the surgical site; impaired upper esophageal sphincter (UES) opening; impaired
oral or oral preparatory phases of swallowing; weak or absent pharyngeal clearance
with associated aspiration (48, 49) (117, 118).
The surgical approach
to C2-C3 is usually above the cranial nerve that moves the tongue, via an incision
from the mastoid tip to the hyoid. Operations on the upper cervical vertebrae
are associated with a higher incidence of disorders involving the oral and oral
preparatory phases of swallowing. Approaches to C4-C7 require retraction of the
carotid sheath and accompanying cranial nerves posterolaterally and retraction
of the aerodigestive tract and larynx medially. At the higher levels (C3-C4) the
superior laryngeal nerve and the hypoglossal nerve are at risk; at lower levels
(C5-C7) the recurrent nerve is more vulnerable to injury. Right-sided anterior
approaches to the cervical spine -- preferred by right-handed surgeons -- are
associated with a higher incidence of inferior laryngeal nerve injury than left-sided
incisions (50) (119). Cadaver dissections provide a likely explanation: there
is less "slack" in the right inferior laryngeal nerve; hence, self-retaining
retractors used to provide exposure to the cervical vertebrae are more prone to
cause stretch injury to this structure.
Dysphagia and aspiration following
anterior cervical spine surgery is common, underdiagnosed, and not well understood.
Initial studies concentrated on injury to laryngeal innervation. More recent work
confirms that edema at the operative site and injury to cranial nerves IX, X and
XII contribute to these adverse outcomes. However, a more important and pervasive
explanation may be denervation of the pharynx, i.e., disruption of connections
between nerves of the pharyngeal plexus and the pharyngeal muscle fibers they
innervate (47). Blunt dissection of tissue planes and retraction of neck structures
to provide operative exposure may well be the basic underlying mechanism for dysphagia,
with injury to specific cranial nerves or their more distal branches adding anatomic
and physiologic specificity to the complication
References
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Trauma
