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BNumb Chin[ Syndrome: Mental Nerve Mononeuropathy Resulting From a Synovial Temporomandibular Cyst Myron M. LaBan, MD, MMSc, Ay-Ming Wang, MD, Andrew Chrisman, MD, and Adam Lenger, MD From the Departments of Physical Medicine and Rehabilitation (MML, AC), Diagnostic Radiology, Section of Neuro-Radiology (A-MW), and Diagnostic Radiology, Section of Musculoskeletal Radiology (AL), Oakland University William Beaumont School of Medicine, Royal Oak, Michigan. Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article. 0894-9115/15/9407-e65 American Journal of Physical Medicine & Rehabilitation Copyright * 2015 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/PHM.0000000000000283
A
66-yr-old man presented to the emergency center of a local hospital with a 4-day history of right-sided chin, lower lip, and dental numbness starting abruptly after eating a banana. He also had a history of atrial fibrillation treated with anticoagulation therapy. Aside from right temporomandibular joint (TMJ) pain and decreased sensation over the chin and right lower lip, the result of his neuromusculoskeletal examination was otherwise normal. Imaging studies, that is, computed tomography and magnetic resonance imaging with contrast, demonstrated osteoarthritis of the right TMJ and a cystic structure medial to the joint, displacing the pterygoid musculature (Fig. 1). Mental nerve mononeuropathy, that is, the numb chin syndrome, presents as a complaint of a loss of sensation of the chin and lips as well as the oral cavity. Although a relatively uncommon complaint, it is well recognized oncologically in its all-too-frequent association with lymphoma and/or metastatic breast cancer.1 In most of these cases, there is already a history of a primary cancer, although it can also be the first symptom of an occult malignancy. The differential diagnoses in a patient with complaints of numb chin syndrome include, among others, a dental infection, localized trauma, malignancy, and/or psychogenic-related pathology. The inferior alveolar nerve branch of the trigeminal nerve terminates distally within the mandible as the mental nerve, supplying sensation to the chin and lower lip. Compromise of this nerve can occur intracranially and/or extracranially. Intracranially, the trigeminal nerve is most often compromised by meningeal carcinomatosis and/or the nerve
All correspondence and requests for reprints should be addressed to: Myron M. LaBan, MD, MMSc, Department of Physical Medicine and Rehabilitation, Oakland University William Beaumont School of Medicine, 3601 W 13 Mile Rd, Royal Oak, MI 48073.
FIGURE 1 Contrast-enhanced magnetic resonance imaging of a synovial cyst of the right TMJ (arrow).
itself can be directly infiltrated by cancer cells.2 In these instances, other cranial nerves may also be affected. Of the reported cases, 36% have involved the trigeminal nerve root and 50% were metastatic to the inferior alveolar nerve within the mandible.3 However, as this case illustrates, other mechanical causes including that of a TMJ cyst can also occur. Synovial cysts of the TMJ are relatively rare with only 38 cases reported, most of which were in female subjects. They usually present as a fluid-filled lesion protruding laterally into the parotid region owing to a herniation of the joint’s synovial lining in response to increased intra-articular pressure due to direct trauma and/or arthritis.4 Magnetic resonance imaging of the brain and/or computed tomography of the mandible can be diagnostic. Treatment remains that of surgical excision.
REFERENCES 1. Smith SF, Blackman G, Hopper G: Numb chin syndrome: A non-metastatic neurological manifestation of malignancy. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:e53Y6 2. Evans RW, Kirby S, Purdy A: Numb chin syndrome. Headache 2008;48:1520Y4 3. Lossos A, Siegal T: Numb lip syndrome in cancer patients: Etiology, response to treatment and prognostic significance. Neurology 1992;42:1181Y4 4. Neis J, Thrani M, Dornhoffer JL: Synovial cyst of the temporomandibular joint: An unusual presentation. Int Adv Otol 2010;6:116Y9
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BNumb Chin[ Syndrome: Mental Nerve Mononeuropathy Resulting From a Synovial Temporomandibular Cyst Myron M. LaBan, MD, MMSc, Ay-Ming Wang, MD, Andrew Chrisman, MD, and Adam Lenger, MD From the Departments of Physical Medicine and Rehabilitation (MML, AC), Diagnostic Radiology, Section of Neuro-Radiology (A-MW), and Diagnostic Radiology, Section of Musculoskeletal Radiology (AL), Oakland University William Beaumont School of Medicine, Royal Oak, Michigan. Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article. 0894-9115/15/9407-e65 American Journal of Physical Medicine & Rehabilitation Copyright * 2015 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/PHM.0000000000000283
A
66-yr-old man presented to the emergency center of a local hospital with a 4-day history of right-sided chin, lower lip, and dental numbness starting abruptly after eating a banana. He also had a history of atrial fibrillation treated with anticoagulation therapy. Aside from right temporomandibular joint (TMJ) pain and decreased sensation over the chin and right lower lip, the result of his neuromusculoskeletal examination was otherwise normal. Imaging studies, that is, computed tomography and magnetic resonance imaging with contrast, demonstrated osteoarthritis of the right TMJ and a cystic structure medial to the joint, displacing the pterygoid musculature (Fig. 1). Mental nerve mononeuropathy, that is, the numb chin syndrome, presents as a complaint of a loss of sensation of the chin and lips as well as the oral cavity. Although a relatively uncommon complaint, it is well recognized oncologically in its all-too-frequent association with lymphoma and/or metastatic breast cancer.1 In most of these cases, there is already a history of a primary cancer, although it can also be the first symptom of an occult malignancy. The differential diagnoses in a patient with complaints of numb chin syndrome include, among others, a dental infection, localized trauma, malignancy, and/or psychogenic-related pathology. The inferior alveolar nerve branch of the trigeminal nerve terminates distally within the mandible as the mental nerve, supplying sensation to the chin and lower lip. Compromise of this nerve can occur intracranially and/or extracranially. Intracranially, the trigeminal nerve is most often compromised by meningeal carcinomatosis and/or the nerve
All correspondence and requests for reprints should be addressed to: Myron M. LaBan, MD, MMSc, Department of Physical Medicine and Rehabilitation, Oakland University William Beaumont School of Medicine, 3601 W 13 Mile Rd, Royal Oak, MI 48073.
FIGURE 1 Contrast-enhanced magnetic resonance imaging of a synovial cyst of the right TMJ (arrow).
itself can be directly infiltrated by cancer cells.2 In these instances, other cranial nerves may also be affected. Of the reported cases, 36% have involved the trigeminal nerve root and 50% were metastatic to the inferior alveolar nerve within the mandible.3 However, as this case illustrates, other mechanical causes including that of a TMJ cyst can also occur. Synovial cysts of the TMJ are relatively rare with only 38 cases reported, most of which were in female subjects. They usually present as a fluid-filled lesion protruding laterally into the parotid region owing to a herniation of the joint’s synovial lining in response to increased intra-articular pressure due to direct trauma and/or arthritis.4 Magnetic resonance imaging of the brain and/or computed tomography of the mandible can be diagnostic. Treatment remains that of surgical excision.
REFERENCES 1. Smith SF, Blackman G, Hopper G: Numb chin syndrome: A non-metastatic neurological manifestation of malignancy. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:e53Y6 2. Evans RW, Kirby S, Purdy A: Numb chin syndrome. Headache 2008;48:1520Y4 3. Lossos A, Siegal T: Numb lip syndrome in cancer patients: Etiology, response to treatment and prognostic significance. Neurology 1992;42:1181Y4 4. Neis J, Thrani M, Dornhoffer JL: Synovial cyst of the temporomandibular joint: An unusual presentation. Int Adv Otol 2010;6:116Y9
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