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A 60-year older man was
presented to the hospital with a complaint of medically refractory,
non-productive cough from past 15 years. Any viral rash, trauma, respiratory
tract infection or exposure to harsh fumes did not precede the cough. The
patient had no history of allergy, asthma or acid reflux. Initially, the cough
was mild, but with time it became more frequent, severe and occurred for a
longer duration. Sometimes, the cough was severe enough to faint him and wake
him up from sleep. The cough used to happen spontaneously, but many activities
like exercise, singing, laughing or exercise triggered the cough. The patient
reported his voice to be normal in between the episodes of coughing. The
patient did not have throat pain; choking or spasm of vocal cords. He reported
that coughing had significantly affected his work and he was unable to work in
2016. In 2018, an improvement in symptoms of cough occurred for a few months,
and it relapsed again. The patient had a history of angina. Three cardiac
stents with clopidogrel were inserted. In 1962 and 1965, the patient has a
tonsillectomy and myringotomy. In 1977, he quit smoking. His reports of all
allergy testing and methacholine challenge had been negative. He was not able
to tolerate pH monitor due to a strong gag reflex but was not even benefitted
with pantoprazole 40 mg and chronic antacids. After being coughing for more
than 10 years, treatment with ACE inhibitor, ramipril for hypertension was
initiated. After 3 months, it was discontinued as it provided no benefit to the
patient. His chest CT was found to be normal. Investigations performed after
multiple consultations with the physicians (allergist, cardiologist, pulmonologists,
otolaryngologist) were also negative.
What
could be the most likely diagnosis of this case presentation?
Introduction:
Neurogenic cough, as
defined by Altman et al. in his latest review, is a chronic cough for more than
eight weeks without external stimuli to the cough mechanism. This could be
defined as an excluded diagnosis which is made after complete investigation to
reduce the chances of other causes. As per the American College of Chest
Physicians (ACCP), the possible reasons to be included are asthma, nonasthmatic
eosinophilic bronchitis, gastroesophageal reflux disease and sinonasal disease.
The latest theories on the etilogy of a neurogenic cough have shown some similarities with trigeminal neuralgia, due to which vascular compression of a vagus nerve rootlet could be the possible cause of neurogenic cough. Trigeminal neuralgia is most commonly caused by the compression of the trigeminal vessel. Anti-neuralgic medicines pharmacologically manage it while microvascular decompression is the possible neurosurgical care. The patients who are not able to take medication due to poor tolerance or side effects are advised for surgical care. Neurogenic cough can be managed with medications like amitryptiline, tramadol, gabapentin, tramadol and non-conventional approaches like speech therapy. A group of patients with neurogenic cough may develop VANCOUVER syndrome (Vagus Associated Neurogenic Cough due to Unilateral Vascular Encroachment of its Root). If the patient is not responding to the pharmacological treatment, microvascular decompression could be tried for subsequent benefit.
A rare case of unilateral vascular compression of a vagus nerve rootlet at the brainstem resulting in the neurogenic cough has been presented. No previous research has reported this etiology of the neurogenic cough. The case study described the features of the patient's cough and his response to numerous treatments. Imaging and surgical outcomes have also been presented. The treatment model for the rare disease condition has been introduced.
A
60 year old man diagnosed with unilateral vascular compression of a vagus nerve
rootlet at the brainstem resulting in the neurogenic cough was recovered after
neurosurgical microvascular decompression of that nerve.
The patient had a
history of angina for which three cardiac stents with clopidogrel were inserted.
On physical
examination, no abnormalities in cranial nerves and lymphadenopathy were
observed. On nasal examination, no signs of sinonasal disease were present.
Laryngoscopy was conducted and revealed normal findings, i.e. normal mucosal
wave, no masses, normal vocal cord closure with a small gap posteriorly, normal
mobility bilaterally, no post-cricoid or arytenoid edema or erythema and no
supraglottic hyperfunction. The score of cough severity index (CSI) 1 was 20
out of 40, and the score of the Leicester quality of life Cough Questionnaire
(LCQ) 2 was 93 out of 133. The reflux symptom index and voice handicap index
were found to be normal at 11/45 and 0/40.4, respectively.
A trial with
carbamazepine 200 mg once a day was stated and post one week, the dose was
increased to 200 mg twice a day. The frequency and intensity of the cough was
greatly reduced (80%) in the second week. But, due to the significant
side-effects of carbamazepine (emotional lability, suicidal ideation, etc.), it
has to be stopped, and relapse of the cough occurred. Psychiatric consultation
showed no signs of depression post-termination of carbamazepine. Also, no signs
of past psychopathy, malingering or conversion disorder were observed. Based on
the outcomes of the first trial, gabapentin and amitryptiline trial was
rejected. The latest experience of researchers related to cough linked with
Hemi-laryngopharyngeal spasm due to vascular compression of the vagus nerve
rootlets provoked them to perform brain MRI in the patient. A unilateral
vascular encroachment of a vagus nerve rootlet at the left brainstem was
revealed as per CISS sequence. The cough halted for almost 8 hours via
breathing humidified air with 5cc of nebulized 1% lidocaine. However, there was
no benefit with first left and post-1 week right unilateral superior laryngeal
nerve block. A severe attack of a rootlet of the left vagus nerve by a loop of
the posterior inferior cerebellar artery (PICA) was confirmed by the
neurological examination of the left lower brainstem.
The procedure involving
microvascular decompression was carried out. PICA was moved away from the vagus
and was anteromedially secured with Teflon and Tiseel. In the postoperative
recovery room, the patient had coughing, but his cough was completely gone
after a few hours. He was able to project his voice and even sign without
coughing. For the past one year, the patient remained free from his previous
pathological cough. His quality of life (depicted by higher LCQ scores) and
severity of cough (described by lower CSI scores) were significantly improved.
He did not experience ant postoperative dysphonia, limb dysmetria, dysphonia or
dysarthria. Normal vocal cord function was observed in the laryngoscopy,
conducted after six weeks of operation.
The case study
presented was a rare disease condition in which the vascular compression of a
vagus nerve rootlet triggered a chronic, non-productive neurogenic cough. The
cough responds well to antineuralgia treatment while it is unmanageable with
anti-reflux medicines, speech therapy, antibiotics and psychotherapy. The cough
progresses continually but with some relief and lapses like trigeminal
neuralgia. MRI showing a vascular compression of the vagus and unilateral benefit
from a vagus nerve block will confirm the diagnosis of this rare condition. The
disease condition can be cured, but neurosurgery near the brainstem is related
to significant risks.
The present case may
provide preliminary guidance on the symptoms and pathophysiology of this rare
disease condition. However, the further case series will confirm the findings.
The disease being unmanageable with the numerous medical therapies and the
absence of any psychiatric history decreases the chances of observed outcomes
due to the placebo effect. A specific test for detecting patients with chronic
cough from etiology other than the incidental contact of a vessel against vagus
nerve will be needed. The sequential unilateral proximal vagus nerve block
could be the valid diagnostic test. The suspension of cough post unilateral
vagus nerve block ipsilateral but not contralateral to an MRI affirmed vascular
compression to be the diagnostic test of choice for VANCOUVER syndrome. In the
present case, unilateral bronchial ventilation with lidocaine and unilateral
superior laryngeal nerve block were tried for symptom elimination. The
diagnosis could have been confirmed by the unilateral positive response, but
the negative one failed to rule it out.
The patient before the
surgery had a clearing understanding about the fact that the decompression of
the vessel impinging his left vagus nerve may not have ceased his coughing. Post-vascular
compression of the trigeminal nerve, focal demyelination at the compression
site may occur supporting ephaptic transmission from nerve fibers conveying
touch (Aβ) to those fibers carrying sharp or burning pain. The tracheobronchial
sensory and laryngeal afferents via vagus nerve move to the brainstem. Similarly,
vagus compression could provide ephaptic transmission from fibers carrying
information from non-cough receptors to those from cough receptors. The vagus
nerve also carries motor fibres apart from 80% sensory fibres. The patient
would come up with coughing and Hemi-laryngopharyngeal spasm if ephaptic
transmission of electrical signals moving in the vagus nerve crossed over to
those motor fibers.
The findings of this
case suggest the need to evaluate patients presented with medically refractory,
no productive cough, for unilateral vascular compression of a vagus nerve. It
also provides preliminary guidance on the symptoms, pathophysiology and
treatment of the rare disease condition.
The Annals of otology, rhinology, and laryngology
Vagus Associated Neurogenic Cough Occurring Due to Unilateral Vascular Encroachment of Its Root: A Case Report and Proof of Concept of VANCOUVER Syndrome.
Honey CR et al.
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