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\begin{document}

\title{A CASE OF VAGAL CEPHALGIA AS A MANIFESTATION OF A LUNG NEOPLASM -- A
CASE REPORT AND REVIEW OF LITERATURE}



\author[1]{Vivek Sanker}%
\author[2]{Sanjana Devaragudi}%
\author[3]{Sanobar Shariff}%
\author[4]{Sheryl  Deva}%
\author[5]{Robert Mathew}%
\author[6]{Umang  Gupta}%
\affil[1]{Noorul Islam Institute of Medical Science and Research Foundation Medicity}%
\affil[2]{Apollo Institute of Medical Sciences and Research}%
\affil[3]{Yerevan State Medical University Named after Mkhitar Heratsi}%
\affil[4]{Kamineni Academy of Medical Sciences and Research Centre}%
\affil[5]{Sree Mookambika Institute of Medical Sciences}%
\affil[6]{Nepalgunj Medical College}%


\vspace{-1em}



  
  \date{May 23, 2024}


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\selectlanguage{english}
\begin{abstract}
Lung cancer can present with unilateral atypical facial pain, a rare
symptom due to vagus nerve involvement or paraneoplastic syndrome. This
manifestation is usually missed, delaying the diagnosis and prognosis.
We discuss a case of a 45-year-old male who presented with right-sided
hemifacial pain and with normal neurological investigations.%
\end{abstract}%



\sloppy


\textbf{A CASE OF VAGAL CEPHALGIA AS A MANIFESTATION OF A LUNG NEOPLASM
-- A CASE REPORT AND REVIEW OF LITERATURE}

\textbf{Vivek Sanker\textsuperscript{1,2}, Sanjana
Devaragudi\textsuperscript{2,3}, Sanobar Shariff \textsuperscript{2,4},
Sheryl Deva\textsuperscript{2,5}, Robert Mathew\textsuperscript{2,6},
Umang Gupta\textsuperscript{2,7}}

\textsuperscript{1}Noorul Islam Institute of Medical Sciences,
Trivandrum, India

\textsuperscript{2}Team Erevnites, India

\textsuperscript{3}Department of General Medicine, Apollo Institute of
Medical Sciences and Research, Hyderabad

\textsuperscript{4} Yerevan State Medical University, Armenia

\textsuperscript{5}Kamineni Academy of Medical Sciences and Research
Centre, India

\textsuperscript{6} Professor, Department of Neurology, Sri Mookambika
Institute of Medical Sciences, India

\textsuperscript{7}Nepalgunj medical college, BP Chowk-12, Nepalgunj
Banke, Nepal.

\textbf{Corresponding author:}

Umang Gupta

Nepalgunj medical college, BP Chowk-12, Nepaligunj Banke, Nepal

Email: dr.umaang@gmail.com

ORCID: 0000-0002-7911-8663

\textbf{ORCID Ids:}

Vivek Sanker: 0000-0003-0615-8397

Sanjana Devaragudi: 0000-0002-9667-8590 Sheryl Deva: 0000-0001-9525-9995
Sanobar Shariff: 0000-0002-2915-958X

\textbf{KEYWORDS:} Facial pain, Lung cancer, Vagal cephalgia, Vagus
nerve

\textbf{INTRODUCTION:}

Unilateral facial pain has many medical and dental causes, like cluster
headaches, trigeminal neuralgia, giant cell arteritis, temporomandibular
joint dysfunction, oral abscess, dental decay, etc. However, when there
is no definitive aetiology, it may be described as ``Atypical facial
pain'' {[}1{]}. De Prez and Freemon reported the first case of atypical
facial pain in association with lung cancer in 1983 {[}2{]}. Since then,
cases have been reported where Facial pain was the first presenting
symptom of Lung cancer. To our knowledge, there are 40 cases of this
manifestation in the literature.

The term ``Vagal Cephalgia'' was first proposed by Evans for the facial
pain and headache associated with non-metastatic lung cancer due to
vagal nerve stimulation. This pain is usually persistent and severe. It
is most commonly around the ear, jaw, and temporal region. Lung cancer
is not always discovered on initial chest radiographs {[}3{]}.
Therefore, physicians do not widely recognize lung cancer presentation,
delaying the diagnosis and increasing morbidity and mortality {[}4{]}.
We describe a case of a patient with lung cancer who presented with
unilateral facial pain.

\textbf{CASE REPORT:}

Presentation and history of symptoms

The patient is a 45-year-old businessman with no history of Hypertension
or Diabetes mellitus. There is no history of cancer in his family. He is
an occasional smoker. The patient presents with pain on the right side
of the face and hoarseness of voice for the past month. The patient also
complained of losing appetite and weight for the past three months. The
hemifacial pain had an insidious onset and was gradually progressing.
The patient described it as a ``constant, dull ache.'' It was more
prominent over the molar region, jaw, ear, and neck, all on the right
side. Suspecting dental cause, he even underwent tooth extraction but
had no relief.

There is no history of eye congestion or numbness of the face. No
earache, tinnitus, or hearing loss was observed. The pain was not
precipitated by chewing/swallowing. There is no positive history of jaw
claudication, myalgias, or visual changes. No phonophobia or photophobia
with vomiting and no family history of headache was observed. There was
no history of cough, dyspnoea, haemoptysis, and epistaxis. There was
also no history of memory loss, behavioural disturbances, dysphagia,
dysarthria, or cranial nerve (CN) deficits. Motor, sensory deficits, or
ataxia was not found. There was no history of fever, diarrhoea, melaena,
or jaundice in the anamnesis.

General and organ-specific examinations

On general examination, the patient was afebrile. The pulse was
88/minute, and blood pressure (BP) was 150/90 Hg. There was no sign of
pallor, clubbing, icterus, or lymph node enlargement. There was no scalp
tenderness. The systemic examination started with the cardiovascular
system, and the first and second heart sounds were normal. In the
respiratory system, the lung fields were clear. Per abdominal
examination, no hepatosplenomegaly or masses/free fluid was found. There
was mild hoarseness of voice with the uvula in the central position. The
palatal movements and gag reflex were normal. There were no abnormal
tongue movements, motor/sensory deficits/cerebellar signs, or neck
stiffness. The skull and spine appeared normal, and the Hypo Geomagnetic
field (HMF) was normal. In the ophthalmological examination, the fundus
appeared normal. The extraocular movements and corneal/conjunctival
reflex were normal. There was no abnormal sensation over the face or
paresis of muscles of mastication.

Investigations

The Erythrocyte Sedimentation Rate (ESR) was 44 mm at 1 Hr. The
remaining blood investigations were normal. The CSF study showed Protein
at 22, glucose was 94, and no abnormal cells were found. The CSF
cytology showed no malignant cells. The Computed Tomography (CT) scan of
the brain showed a hypodense lesion in the Left Occipital region (Figure
1). An MRI scan of the neck and mediastinum was performed to rule out
structural causes for the hoarseness of the voice\emph{.} After
extensive imaging, no structural cause of hemifacial pain syndrome was
found. The ENT consultation revealed right vocal cord palsy. Given the
suspicious cerebral lesion search for primary malignancy was made. CECT
scan of the thorax showed a relatively well-defined enhancing soft
tissue density lesion in the right lung with contiguous mediastinal
lymphadenopathy (Figure 2). Squamous cell carcinoma was confirmed to be
the diagnosis after the biopsy.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

Figure 1. CT Brain: showed a hypodense lesion in the Left Occipital
region (d/d: infarct, space-occupying lesion (SOL))\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

Figure 2: Contrast-enhanced Computed Tomography (CECT) Thorax: A
relatively well-defined enhancing soft tissue density lesion in the
right lung with contiguous mediastinal lymphadenopathy

\textbf{DISCUSSION:}

Our patient had a lung malignancy presenting as hemifacial pain syndrome
and vocal cord palsy. In addition, the pain had the features of vagal
cephalalgia, a type of atypical facial pain syndrome.

This facial pain is characterized by its unilateral nature, an aching
quality that worsens over minutes and is localized around the ear, jaw,
and temple. One of the causes of this type of pain is lung cancer, with
the pain occurring ipsilateral to the cancer site, showing a dextral
dominance {[}5{]}

The clinical characteristics of several documented cases of facial pain
associated with lung cancer can be found in the literature. The ear, the
mandible, and the temporal region are the most typical locations for
face pain, which is nearly invariably unilateral. The discomfort may be
constant or intermittent and is commonly described as intense and
painful. Digital clubbing, an elevated ESR, and hypertrophic osteopathy
may also influence the diagnosis. Treatment of face pain with
radiotherapy and tumor removal via vagotomy is quite successful. Lung
cancer should be considered when making a differential diagnosis for
facial pain that is unusual or unresponsive to treatment. Face pain
related to non-metastatic lung cancer may be caused by referred pain
from vagal nerve invasion or compression and paraneoplastic syndrome
brought on by the generation of circulatory humoral factors by the
cancerous cells.

This is an uncommon presentation of lung malignancy. This pain arises as
a referred pain from the lung via the vagus nerve. The visceral and
somatic afferents terminate in the trigeminal nucleus. Due to the
convergence of somatic and visceral afferents in the central nervous
system (CNS), visceral pain is referred to as the somatic segment where
they enter the CNS. Dextral dominance can be explained by the
relationship of the right vagus nerve with the main bronchus and
trachea, as the tumor can directly infiltrate the nerve.

In contrast, the left vagus is separated by the great vessels. Afferent
impulses travel via the visceral afferents and connect with their
somatic counterparts. Due to the extensive synapsing of cranial nerves
V, VII, IX, and X in the trigeminal nucleus, a larger area of the face
can be involved {[}6{]}.

Sarlani E et al. also postulated the role of circulating humoral factors
produced by the tumor causing a paraneoplastic syndrome as a possible
explanation of facial pain in lung carcinoma {[}7{]}.

A few similar cases in the literature are described below:\selectlanguage{english}
\begin{longtable}[]{@{}llllll@{}}
\toprule
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Study; Country; year\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Demographic features\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Past History\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Duration of illness\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Investigations\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Treatment given\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
A case of intractable facial pain secondary to metastatic lung cancer;
Italy;2008 {[}8{]}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
70-year female\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Non smoker\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
15-month history of constant facial pain.\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Clinical examination: abnormal breath sounds, loss of sensation on right
side of face. Chest X-ray: mass in right hilar region\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Treatment with amitriptyline 40 mg/day and gabapentin (up to 2000
mg/day) was not successful. Pain resolved with radiation therapy and
chemotherapy.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Lung cancer presenting with unilateral facial pain: remission after
laryngeal nerve palsy; Italy;2006 {[}9{]}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
39-year female\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Smoked 1 pack of cigarettes a day for 20 years.\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
2-month history of facial pain on the left side.\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Clinical examination: Supraclavicular lymphadenopathy CT scan chest:
Mass in left mediastinum.\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Gabapentin, carbamazepine, and prednisone did not relieve pain. The
patient was treated with chemotherapy: gemcitabine and cisplatin\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
A review of intractable facial pain secondary to underlying lung
neoplasms, USA;2003 {[}10{]}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
63-year-old male\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
65 pack-year history of smoking\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
5 weeks of facial pain\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
ESR elevated Chest X-ray: right hilar mass.\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Opioids were unsuccessful. Treated with radiation and
chemotherapy.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Facial pain as the presenting symptom of lung carcinoma with normal
chest radiograph; USA,2003 {[}1{]}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
52-year-old man\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Smoked 3 packs of cigarettes per day for 40 years. Family history of his
father having died of lung cancer.\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
6 months of sharp facial pain\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
WBC count elevated Chest X-Ray: Right lower lobe mass.\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Pain did not reduce with NSAIDs and narcotic analgesics. Did not respond
to radiation therapy.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Facial pain as the presenting symptom of lung carcinoma with normal
chest radiograph; USA;2003 {[}1{]}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
63-year-old male\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
History of left lower lobectomy for adenocarcinoma- of the lung. 120
pack-year smoking history.\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
1-month history of progressive pain\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
ESR elevated. CT chest: subcarinal mass\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Radiotherapy.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Persistent unilateral facial pain in lung cancer patients with
mediastinal nodal involvement; UK;2013 {[}4{]}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
62-year-old man\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
History of wedge resection for lung cancer.\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
After 5 months of resection, he developed facial pain.\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
CT, MRI showed mass in lung and brain\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Opioids, NSAIDs and neuropathic adjuvants failed. Palliative
radiotherapy and cisplatin -- etoposide chemotherapy relieved the
pain.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Persistent unilateral facial pain in lung cancer patients with
mediastinal nodal involvement; UK;2013 {[}4{]}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
65-year-old woman\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
No\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
12 months history of right jaw pain\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Investigations revealed a T4NXM0 squamous cell carcinoma of the lung.
She was given palliative radiotherapy to the chest, 36 Gy in 12
fractions\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Amitriptyline gave little pain relief. Palliative radiotherapy to the
chest completely resolved the pain.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Facial pain associated with lung cancer: a case report;1983
{[}2{]}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
45-year-old male\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
No\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
4 months of deep, boring pain near maxilla\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
ESR elevated Chest X ray: mass in right lower lobe\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Ibuprofen, carbamazepine and diphenhydramine Hydrochloride did not
reduce pain but, aspirin and acetaminophen did. Pain completely resolved
on surgical resection.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Unilateral facial pain as the first symptom of lung cancer: are there
diagnostic clues? Belgium;1992 {[}11{]}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
53-year-old\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Smoker\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
12-month history of facial pain\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Adenocarcinoma of the right superior lobe was diagnosed\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Pain was not relieved by analgesics and sphenopalatine ganglion
anaesthesia. Radiotherapy completely resolved pain.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Facial pain as a symptom of nonmetastatic lung cancer; USA;1995
{[}5{]}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
68-year-old woman\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
40 pack year smoking history\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
1-year history of right sided facial pain\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Clubbing present Chest X ray: Middle lobe nodular infiltrate\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
The pain did not respond to amitriptyline, narcotic medications,
carbamazepine, phenytoin. Radiotherapy and chemotherapy resolved
pain.\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

For diagnosis of atypical facial pain (ATFP), the international
classification of headache disorders has described the following
criteria {[}12{]}:

1. Facial pain recurring for more than 2 hours in a day for a period of
3 months

2. Poorly localized, dull aching, or nagging pain

3. Clinical neurological examination and dental examination are normal

Physicians still diagnose atypical facial pain by exclusion as all these
symptoms are nonspecific. A complete clinical examination must rule out
other causes like dental infections, vascular factors, craniofacial
tumors, trigeminal neuralgia, and migraine. Radiological diagnosis,
including computed tomography or magnetic resonance imaging, should
support the diagnosis {[}12,13{]}. Especially if the patient is a
smoker, a chest radiograph is essential to rule out lung neoplasms
presenting as facial pain {[}6{]}

Thus, a multidisciplinary approach is essential for the diagnosis of
atypical facial pain {[}14{]}

Treatment of ATFP is often unsatisfactory, so patient education often
becomes essential {[}15{]}. Antidepressants {[}4{]}, which include
amitriptyline, duloxetine, venlafaxine, and Anticonvulsants {[}10{]}
(carbamazepine, oxcarbazepine, phenytoin, gabapentin, lamotrigine) have
been used to treat ATFP. Other agents that give relief are botulinum
toxin A, local anaesthetics like lignocaine, muscle relaxants
(baclofen), phentolamine, and selective serotonin receptor agonists
(sumatriptan) {[}16{]}. As this is neuropathic pain, high-frequency
repetitive transcranial magnetic stimulation (rTMS) on the right
somatosensory cortex aborted pain significantly {[}17{]}. Chemotherapy
is the least effective {[}15{]}. Radiotherapy, vagotomy, and tumor
resection are the standard forms of treatment for ATFP {[}7{]}. Patients
respond excellently to resection, but surgery is not possible due to
delayed diagnosis as 79 of patients have had a regional spread.
Radiation therapy also helps to ameliorate pain, but the response occurs
over months. Most patients die before pain relief is obtained {[}15{]}.

\textbf{CONCLUSION:}

Early detection of lung carcinoma has to be accomplished to prevent
morbidity and mortality, and atypical facial pain should be considered a
possible manifestation.

\textbf{CONFLICTS OF INTEREST:}

None declared.

\textbf{AUTHOR CONTRIBUTION:}

All the authors contributed equally in drafting, editing, revising and
finalizing the case report.

\textbf{ETHICAL APPROVAL:~}

The ethical approval was not required for the case report as per the
country's guidelines.

\textbf{CONSENT:}

Written informed consent was obtained from the patient to publish this
report.

\textbf{DATA AVAILABILITY STATEMENT:}

The data that support the findings of this article are available from
the corresponding author upon reasonable request.

\textbf{References:}

1. Abraham PJ, Capobianco DJ, Cheshire WP. Facial pain as the presenting
symptom of lung carcinoma with normal chest radiograph. Headache
{[}Internet{]}. 2003;43(5):499--504. Available
from:\emph{http://dx.doi.org/10.1046/j.1526-4610.2003.03097.x}

2. Des Prez RD, Freemon FR. Facial pain associated with lung cancer: a
case report. Headache {[}Internet{]}. 1983;23(1):43--4. Available
from:\emph{http://dx.doi.org/10.1111/j.1526-4610.1983.hed2301043.x}

3. Evans RW. Hemicrania Continua-like headache due to nonmetastatic lung
cancer--a vagal cephalalgia. Headache {[}Internet{]}.
2007;47(9):1349--51. Available
from:\emph{http://dx.doi.org/10.1111/j.1526-4610.2007.00936.x}

4. Pembroke CA, Byrne A, Lester JF, Button M. Persistent unilateral
facial pain in lung cancer patients with mediastinal nodal involvement.
Lung Cancer {[}Internet{]}. 2013;82(1):173--5. Available
from:\emph{http://dx.doi.org/10.1016/j.lungcan.2013.06.024}

5. Capobianco DJ. Facial pain as a symptom of nonmetastatic lung cancer.
Headache {[}Internet{]}. 1995;35(10):581--5. Available
from:\emph{http://dx.doi.org/10.1111/j.1526-4610.1995.hed3510581.x}

6. Bindoff L, Heseltine D. Unilateral facial pain in patients with lung
cancer: A referred pain via the vagus? Lancet {[}Internet{]}.
1988;331(8589):812--5.Available
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