a 38-year - old male patient with a 40-pack - year history of smoking initially presented with sudden - onset right - sided facial nerve palsy which was diagnosed as idiopathic bell 's palsy and was treated with prednisolone .
three weeks later , the patient developed a new left - sided facial palsy in addition to his unrecovered right - sided facial palsy .
outside of the facial nerve paralysis , he was neurologically intact , and his physical examination revealed no abnormalities .
further workup was carried out to rule out autoimmune , metabolic , infectious , and vasculitic causes and revealed no abnormality .
a chest x - ray showed a right upper lobe opacity which prompted a computed tomography ( ct ) scan of the chest which showed a well - defined , suspected soft - tissue lesion in the right upper lobe with extensive hilar and ipsilateral mediastinal lymphadenopathy ( fig 1a , b ) . at this point , the differential diagnosis included sarcoidosis and primary lung cancer given the presenting complaint was bilateral facial nerve paralysis .
because the intrapulmonary lesion was too distal to be reached by flexible bronchoscopy , video - assisted mediastinoscopy was performed and revealed gross right - sided mediastinal invasion .
multiple biopsies from lymph nodes were taken and revealed metastatic poorly differentiated adenocarcinoma of the lung .
accordingly , positron emission tomography ( pet)/ct and magnetic resonance imaging ( mri ) of the brain were performed to stage the cancer .
brain mri with contrast showed normal enhancement of the seventh and eighth cranial nerves with neither brain metastasis nor leptomeningeal metastasis .
the pet / ct showed a metabolically active right upper lobe lesion with extension into the mediastinum and active ipsilateral mediastinal lymph nodes but no distant metastasis .
due to our high clinical suspicion of leptomeningeal involvement , a lumbar puncture was performed .
at this point , his clinical stage was considered ciiib ; ct4 ( extension ) n2 m0 .
the patient received platinum - based doublet chemotherapy with a total of 60 gray of radiation .
he tolerated the chemotherapy and radiation well but had no resolution of his facial paralysis .
nine months later , the patient presented to the emergency department with severe headache and generalized tonic - clonic seizures . on physical examination
an abdominal and pelvic ct scan was obtained which showed newly developed liver metastases as well .
given the patient 's disease progression and deteriorating condition , palliative care was offered , and the patient succumbed to his disease .
the incidence of leptomeningeal carcinomatosis has been reported to be between 0.8 and 8% in many autopsy studies , though the true incidence is difficult to determine . among
all known solid tumors , leptomeningeal metastasis is more common in breast cancer , lung cancer , and melanoma [ 1 , 2 ] . with improvements in survival rates among patients who have cancer ,
the incidence of leptomeningeal carcinomatosis in patients with non - small - cell lung cancer is increasing .
however , small - cell lung cancer is more likely to cause leptomeningeal metastases with a frequency of 1025% , as compared to 1% in the case of non - small - cell lung cancer .
though leptomeningeal metastasis is a late complication of cancer , it can be the initial presentation in some cases .
our case is one of these cases where neurologic symptoms were the first and only presentation of pulmonary adenocarcinoma . reviewing the literature , and to the best of our knowledge ,
our case is the only case describing bilateral facial nerve palsy as the only manifestation of lung adenocarcinoma .
however , as demonstrated here , patients may present with a single isolated neurological sign or symptom . among these
facial weakness was detected as a sign of an underlying leptomeningeal metastasis in about 13% of cases at the time of presentation .
multiple cases in the literature reported unilateral peripheral facial nerve palsy as the first presentation of an underlying cancer . in some of these cases , the underlying cancer was pulmonary adenocarcinoma .
csf analysis has been considered the gold standard method to diagnose leptomeningeal metastases ; however , the false - negative rate seen in many cases ( even after repeating the lumber puncture ) makes the diagnosis of leptomeningeal metastases challenging , causing many to suggest using mri as well as csf analysis .
csf findings suggestive of leptomeningeal metastases are high cell count , high protein , low glucose , and high csf opening pressure .
mri of the brain is considered more sensitive in leptomeningeal metastases from solid tumors , while csf analysis is superior to mri in cases of hematological malignancies [ 5 , 7 ] .
csf samples are more likely to have positive findings from either clinically or radiographically diseased areas .
our patient 's second csf sample was drawn directly from the ventricles after his disease had progressed , which may have played a role in the positive result of the csf cytology .
all authors have been personally and actively involved in substantive work leading to the manuscript and will hold themselves jointly and individually responsible for its content .
the authors declare that no financial or other conflict of interest exists in relation to the content of this paper .
 leptomeningeal carcinomatosis is rare , and its precise incidence is unknown . it is associated with a wide spectrum of solid and hematological malignancies . to complicate its diagnosis , the clinical presentation of leptomeningeal carcinomatosis can be variable . 
 we report a case of a 38-year - old male with bilateral facial nerve paralysis as first presentation of lung adenocarcinoma . to our knowledge 
 , this is the only case describing bilateral facial nerve palsy as the first and only manifestation of lung adenocarcinoma . 
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