Clinicopathological Study of Parapharyngeal Space Tumor

Objective: To see the mode of presentation, diagnosis and management of parapharyngeal space tumours. Study design: Cross sectional study. Setting: Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh. Methods: The condition being relatively rare, it was difficult to find good number of fresh cases. We have studied all cases of parapharyngeal space tumour attending in the Bangabandhu Sheikh Mujib Medical University from January 2010 to March 2011. Result: Parapharyngeal space tumours are rare head and neck neoplasms.The third decade of life showed greatest incidence. The main presenting complaint’s were painless neck swelling (73%). The highest number of pathology were attached to the deep lobe of parotid gland (pleomorphic adenoma-27%) and then neurofibroma (20%). Of all cases 77% were benign. Their accurate diagnosis and management is challenging.


Introduction:
The parapharyngeal space is a potential space lateral to the pharynx. On each side it contains some vital structures like carotid arteries, internal jugular vein, last four cranial nerves and sympathetic chain.
Parapharyngeal tumours most commonly present as asymptomatic masses in the neck or palatal region found on routine physical examination. Tumor arising in the parapharyngeal space draw special attention because of difficulties in investigation, diagnosis and surgical intervention. Parapharyngeal space tumor are rare, forming less than 0.5% of head and neck neoplasm. [1][2][3][4] . Both benign and malignant tumors may arise from any of the structures contained within the parapharyngeal space, 70-80% are benign and 20-30% are malignant. 1,2,5 . The majority of tumor arising in the parapharyngeal space are benign and surgical resection is the main stay of treatment. 2,6 In this study I attempted to present our experiences regarding presentation, diagnosis and management of these lesions and to compare and contrast other available literature.

Methods:
This study was carried out in the Department of ENT & HNS, Bangbandhu Sheikh Mujib Medical University. We have studied all cases of parapharyngeal space tumour (30 patients) attending in this Department from January 2010 to March 2011. Patients of parapharyngeal space tumour were selected on the basis of clinical presentation, radiological investigations and FNAC reports. Ultrasound of neck and Color Doppler study was done in selected cases.

Result:
In our study, Maximum patients fall within the age group between 21-40 years and among them the most common age group of presentation was 31-40 years ( 10 patients-33%) followed by the age group between 21-30 ( 9 patients-30%). There was male predominance. Out of 30 cases, 16 cases (53%) were males and 14 cases (47%) were females.

Discussion:
The parapharyngeal space is a virtual anatomic region classically compared to an inverted triangular pyramid extending from the skull base to the hyoid bone. Tumour arising in the parapharyngeal space represent a challenge to the head and neck surgeon. Not only because they are rare, but also because of the wide variety of histological types in this site.
This study as it comprises of cases attending hospital fifteen months of time limit only, is not large enough to represent scenario with more accuracy. But since it was carried out in a major tertiary health institute of the capital city of a 140 million population country, cases were not difficult to found.  10 Pang, Goh and Tan 4 observed no sex predominance in their series too.
Majority of the patients were from middle socioeconomic class. 25% of them from the affluent and 15% from lower socioeconomic class. 65% of them were from the rural area.
Clinical presentation of the patients were diverse. Most patients presented with multiple complains. The most common presenting symptom was of a painless neck swelling, as in 22 patients (73%) in this study. Next to this oropharyngeal bulging was experienced by 14 of patients (47%). Eleven patients complained dysphagia (37%) and nine patients complained dysphonia (30%). Sorethroat and mild throat discomfort were complained by 6 patients (20%).
Five patients presented with ear symptoms. They had conductive hearing loss due to middle ear effusion subsequent to Eustachian tube blockade 11 caused by the large tumour indenting the nasopharynx.
These tumours are usually painless because of their expansile nature, however, pain must raise a strong suspicion of malignancy.
Speech or swallowing problems may result from lower cranial nerve involvement. It occurs more commonly due to displacement of the lateral pharyngeal wall and the tonsil. In our study, one patient had a tonsillectomy performed for a unilateral " tonsillar" mass. One patient had an incision and drainage performed earlier for a suspected left "quinsy".
In this study salivary gland origin tumours were of the highest incidence 47%. In nine cases the tumours arose from the deep lobe of the parotid gland. Maran 10 observed that deep lobe tumours of the parotid gland account for 12 to 25 percent of all parotid tumours.
In the series reported by Work et al 12 and Mayo clinic 13 the commonest tumours were benign mixed salivary tumours (33.3% and 43% respectively in both the series).
The present study depicted 27% incidence of benign mixed salivary tumour. The cases of ectopic salivary gland tumour were diagnosed as an adenocarcinoma and a mucoepidermoid carcinoma.
Tumour arising from the minor salivary gland tissue within the parapharyngeal space fat 14 have also been documented. These tumours have a higher likelihood of malignancy. 4 Ten(33%) of the cases were of neurogenic tumours. The figure as found by Tincani et al. was 35.3% in his study.
Bahadur, Tandon, Kacker and Mishra reported 13 cases of neurofibroma in their series of 36 cases which constitutes 36% of total cases.
In the present series 4 patients had neurilemmomas. In one case the tumour was attached to hypoglossal nerve from which it difficult to be freed. Patient had temporary post-operative XII th nerve paralysis, which improved subsequently. In another case the fibres of the XII th nerve were found stretched over the capsule of the tumour from which the tumour could be easily dissected and no palsy was occure. In two cases the tumour were attached to the vagus nerve from which the tumour could not be freed easily. They suffered from temporary post-operative vagal paralysis which improved subsequently. Six patients had neurofibromas, from which one patient developed temporary combined IX,X and XI th cranial nerve paralysis.
We had 5 cases (16%) of chemodectomas. Out of them 4 cases were of carotid body tumours and one of vagal body tumour. CT scan or MRI, carotid angiography or MRA and urinary catecholamine level were done for diagnosis. Either contrasted CT or MRI will clearly demonstrate a chemodectoma expanding the carotid bifurcation. 15 Sometimes carotid body tumours may also be malignant with a metastasis rate of 2 to 9 percent. 16 Surgical excision is the treatment of choice and offers high rate of cure 17  Pre-operative assessment by FNAC were confirmed in all cases by histopathological examination. Post operative complications were few. 13% of cases were encountered temporary cranial nerve paralysis, which improved subsequently. Dysphagia were occurred in 10% of cases. One patient developed hematoma, which was managed conventionally.

Conclusion:
Anatomy of parapharyngeal space is complex with important neurovascular structures. Parapharyngeal space tumours are rare and mostly benign. More over, they are difficult to diagnose early as they produce symptoms slowly. Surgical resection being the mainstay of therapy, tumours of this complex anatomical region call for careful preoperative planning and great skill for selecting the right approach and for management with minimal morbidity and recurrence. The present study unfurls the need to carry on with further research into this particular area.