Numb Chin Syndrome Secondary to Vestibular Schwannoma

Numb chin syndrome (NCS) or mental neuropathy is a sensory neuropathy. It can present as trivial finding of hypoesthesia/ paraesthesia or pain over the chin and area supplied by the mandibular nerve. The etiology can vary from dental pathogenesis to malignancy and neurological disorders. Here we present a case report of 18 year old female patient, who presented with numb chin syndrome and on further investigation was detected with a large vestibular schwannoma.


Introduction
Parasthesia or Numbness over the chin is common symptom in dental practice. It is generally seen as adverse effect of peripheral neurectomy that may occur during oral surgical procedures involving inferior alveolar nerve. However, in certain instances it may be symptom of serious underlying disorder such as malignancy or neurological pathology. In this case report we highlight one such case of a young patient presenting with a trivial symptom of numbness over the chin which was the only manifestation of a large intracranial Schwannoma.

Case Report
An 18 year old female patient reported with chief complaint of numbness in the left lower side of the face for 2 months.
Her medical and dental history was not significant. She was well built and nourished, conscious and cooperative during the examination. On extra oral examination there was no facial a symmetry. Temporomandibular examination was normal. A single jugulodigastric lymph node was enlarged and tender on the left side. It was firm in consistency and not fixed. On intraoral examination, two ulcers spherical in shape and less than 1cm in diameter with peri inflammatory halo were noticed on the left lower labial mucosa. Tongue was coated with mild erythematous changes on the left lateral aspect, soft palate and tonsillar pillars on the left side were also erythematous. We performed cranial nerve examination and found deficit on the mandibular division of   In the presence of metastatic disease NCS is an advanced symptom. This symptom is often overlooked or not urgently investigated. It is one of the symptoms with poor prognosis, only 15% of patients are known to survive more than nine months.

NCS has better prognosis if it has leptomeningeal involvement.
Hence the role of dentists, ENT specialists and physicians is to consider malignancies and neurological disorders in patients with NCS in the absence of local causes. Patients need investigation to rule out malignancies and neurological disorder. This involves blood examination and radiographs which include OPG, brain MRI and targeted imaging such as CT scan and scintigraphy [4]. The trigeminal nerve root originates from the lateral aspect of the pons and extends superiorly, laterally and anteriorly towards the petrous apex entering the Meckel's cave. The first segment which extends from the brainstem to the Meckel's cave is referred to as cisternal or cerebellopontine angle segment. The cerebellopontine angle is a triangular space located posterior to the pyramid inferior to the tentorium, lateral to pons and ventral to cerebellum.
The most common mass found in this location is vestibular schwannoma, commonly referred to as acoustic neuroma, followed by meningioma and epidermoid tumors and rarely metastases [5]. Nerve sheath tumors can be dividing into schwannoma, neurofibroma and malignant nerve sheath tumors.  CT imaging displays it as is dense regions difficult to differentiate. Areas within large tumors are hypodense. On administration of contrast it shows moderate enhancement. MRI is the investigation of choice for these lesions. T1-weighted image, it appears as isointense and cystic areas appears hypointense.
T2 images it appears as hyperintense to brain and cystic areas appear hyperintense [11]. Treatment is directed at symptomatic control. Surgical resection of intracranial tumors carries a risk of significant morbidity such as hydrocephalus and meningitis.
Microsurgical techniques have better outcome with preservation of neurologic function. Malignant nerve sheath tumors have poor prognosis [11]. After the neurological evaluation, our patient has been kept under observation, it was considered best not to perform any intervention. Patient has been under continuous follow up and during the preparation of this manuscript she has been found to be stable.

Conclusion
It is important that symptoms of parathesia over the chin are never overlooked as trivial in patients. Investigations such as MRI of brain may reveal an underlying pathology that may be detrimental.