Abstract
Numb chin syndrome (NCS) is characterized by numbness in an area of the chin and lower lip along the distribution of the mental or inferior alveolar nerves, a branch of the mandibular division of the trigeminal nerve. Most cases of NCS are due to diffuse metastatic disease, especially associated with underlying lymphoproliferative and breast cancer. Other less like causes are dental, traumatic, toxic, drug-induced, or infectious. NCS may be the initial symptom of malignancy or metastasis in patients with cancer. Axial and vertebral bone metastases are common in patients with carcinoma of the prostate; however, involvement of the branches of the trigeminal nerve is rare. We present a case of the NCS in a 59-year-old man with metastatic prostate adenocarcinoma to the base of the skull.
Keywords: Numb chin syndrome, Lip numbness, Prostate cancer
Introduction
Numb chin and cheek syndrome (NCS) is a rare syndrome, initially described by Charles Bell in 1830s when he noted absence of sensation in the left lower lip of a patient with breast cancer. NCS usually involves the mental or inferior alveolar nerves, branch of the mandibular division of the trigeminal nerve [1]. Motor function of the lower face is unaffected as it is innervated by the facial nerve.
Case report
A 59-year-old man with history of hypertension, end-stage renal disease s/p right-sided cadaveric renal transplant, and biopsy confirmed prostate adenocarcinoma with generalized (osteoblastic) metastasis was admitted to medicine service for acute renal insufficiency and hematuria. Neurology was consulted as he complained of left lip numbness with mild headache over 2 weeks. Lately, the lip numbness was constant, progressively worsening, and had difficulty eating and drinking as the inside of his left mouth and tongue was numb and he lost considerable weight (43 lbs in 6 months).
Neurologic examination showed decrease sensation on the left lower chin, lip, and inside of his left mouth. Rest of the neurologic examination was normal. Skull X-ray showed diffuse sclerotic osseous metastasis (Figs. 1a and b). CT of maxillofacial without contrast showed extensive osteoblastic metastatic disease in the calvarium, skull base, and facial bones without a pathologic fracture. Metastatic disease particularly involved the left foramen ovale and foramen rotundum along the course of the V3 and V2 nerves (Figs. 2a and b).
Fig. 1.
(a and b) Skull X-ray showed diffuse sclerotic osseous metastasis.
Fig. 2.
Computerize tomography of maxillofacial without contrast shows extensive osteoblastic metastatic disease in the calvarium, facial bones, and skull base involving the left foramen ovale (a, asterisks [*] normal) and foramen rotundum (2) along the course of the V3 and V2 nerves (arrows).
Our patient was started on gabapentin and was discharged to hospice care where he passed away within a week.
Discussion
NCS is a rare syndrome, involves the mental or inferior alveolar nerves, branch of the mandibular division of the trigeminal nerve [1]. It is mainly unilateral but bilateral involvement has been reported in 10% cases [1]. The most common causes of NCS is malignancy due to lymphoproliferative and breast cancer having metastasized to the mandible [2,3]. This NCS case was unique because: first, the mandibular nerve was compressed at the skull base, rather than metastases to the mandible (with compression of the mental or inferior alveolar nerve) being the most common site [4]. Second, skull-based metastases usually involve other cranial nerves specially sixth and seventh, which was absent in this case. Finally, the presence of oral numbness anatomically differentiated it to be a proximal versus distal (mental) involvement of the mandibular division of the trigeminal nerve [5].
Author contributions
Dr. Meheroz H. Rabadi—Study concept and design Data acquisition Analysis and interpretation Write-up of the manuscript for intellectual content Study supervision
Footnotes
Funding: None.
Competing interests: The author reports no disclosures or conflict of interest.
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