title: Diagnostic pitfall: Adenoid cystic carcinoma of the tongue presenting as an isolated hypoglossal nerve palsy, case report and literature review.
abstract: BACKGROUND
  We describe a patient with an unusual presentation of an isolated hypoglossal nerve palsy as a result of perineural invasion (PI) from adenoid cystic carcinoma (ACC). We will also discuss the diagnostic pitfalls as well as present a short literature review of adenoid cystic carcinomas and suggest improvement to the current diagnostic algorithm for isolated hypoglossal nerve palsies.
  
  
  METHODS
  A 63year old Malay female presented with progressive dysphagia and slurred speech for one year. Physical examination showed unilateral right tongue wasting, fasciculation and deviation to the right. An MRI showed atrophy of the tongue due to denervation and subsequently she was treated in a neurology clinic for 8 months. Due to lack of improvement, she was referred to our surgical unit and underwent examination under anaesthesia (EUA) and biopsy. Histology showed adenoid cystic carcinoma with perineural involvement, resulting in lower motor neuron signs. She underwent radiotherapy to the base of her tongue (70Gy/35#). A PET-CT one month post treatment showed complete response.
  
  
  CONCLUSIONS
  Adenoid cystic carcinoma (ACC) is a salivary gland neoplasm. It is characterized by local invasiveness with frequent recurrence and indolent growth. It affects major salivary glands more than minor salivary glands. In malignancies that have a propensity for PI such as ACC, patients may present atypically with nerve palsies. In infiltrative lesions, the primary tumour may not be evident on magnetic resonance imaging. Therefore, to achieve a diagnosis, a high index of suspicion is required. When the diagnosis is in question, deep biopsy and positron emission tomography may be useful.
authors.affiliation: Department of Surgical Oncology, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610. Electronic address: Hide.wee@mohh.com.sg.
authors.forename: Hide Elfrida
authors.initials: HE
authors.lastname: Wee
authors.affiliation: Singapore General Hospital, Outram Rd, Singapore 169608. Electronic address: rafay.azhar@singhealth.com.sg.
authors.forename: Rafay
authors.initials: R
authors.lastname: Azhar
authors.affiliation: Singapore General Hospital, Outram Rd, Singapore 169608. Electronic address: poyin.tang@mohh.com.sg.
authors.forename: Po Yin
authors.initials: PY
authors.lastname: Tang
authors.affiliation: Division of Oncologic Imaging, National Cancer Center Singapore, 11 Hospital Drive, Singapore 169610. Electronic address: patrick.teo.t.h@singhealth.com.sg.
authors.forename: Tze Hern
authors.initials: TH
authors.lastname: Teo
authors.affiliation: Department of Surgical Oncology, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610. Electronic address: gopaliyer@nccs.com.sg.
authors.forename: Narayanan Gopalakrishna
authors.initials: NG
authors.lastname: Iyer
authors.affiliation: Department of Surgical Oncology, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610. Electronic address: tan.hiang.khoon@singhealth.com.sg.
authors.forename: Hiang Khoon
authors.initials: HK
authors.lastname: Tan
authors.affiliation: Department of Surgical Oncology, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610. Electronic address: tan.ngian.chye@nccs.com.sg.
authors.forename: Ngian Chye
authors.initials: NC
authors.lastname: Tan
keywords: Adenoid cystic carcinoma; Case report; Head and neck cancer; Hypoglossal; Isolated twelfth nerve palsy tongue; Lower motor neuron disease