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 Table of Contents  
Year : 2021  |  Volume : 21  |  Issue : 3  |  Page : 308-310

Altered somatosensory processing in secondary trigeminal neuralgia: A case report

1 Department of Oral Diagnostic Sciences, Nihon University school of Dentistry, Tokyo, Japan
2 Department of Diagnostic Sciences, Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, USA

Date of Submission04-Mar-2021
Date of Decision02-May-2021
Date of Acceptance22-Jun-2021
Date of Web Publication10-Aug-2021

Correspondence Address:
Noboru Noma
1-8-13 Surugadai, Chiyoda-Ku, Tokyo
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jips.jips_75_21

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Secondary trigeminal neuralgia might be very rarely preceded by trigeminal neuropathic pain. The patient, in this case, presented with paroxysmal pain in the left mandible and numbness of the lower lip and tongue. Sensory testing of these areas revealed cold and heat hyperalgesia and mechanical hyposensitivity in the mandibular region. Magnetic resonance imaging showed a mass in the left cerebellopontine angle. The patient was prescribed systemic mirogabalin (2.5 mg/day), which provided some relief until the tumor was removed. The histopathological diagnosis was an epidermoid tumor. This article discusses the clinical characteristics and sensory testing findings that distinguish secondary trigeminal neuralgia from trigeminal neuropathic pain based on the International Classification of Orofacial Pain.

Keywords: International Classification of Orofacial Pain, secondary trigeminal neuralgia, sensory testing

How to cite this article:
Noma N, Ozasa K, Young A. Altered somatosensory processing in secondary trigeminal neuralgia: A case report. J Indian Prosthodont Soc 2021;21:308-10

How to cite this URL:
Noma N, Ozasa K, Young A. Altered somatosensory processing in secondary trigeminal neuralgia: A case report. J Indian Prosthodont Soc [serial online] 2021 [cited 2022 Aug 20];21:308-10. Available from: https://www.j-ips.org/text.asp?2021/21/3/308/323592

  Introduction Top

According to the International Classification of Orofacial Pain, space-occupying lesions can cause both secondary trigeminal neuralgia and trigeminal neuropathic pain.[1] The clinical characteristics can help distinguish between the two; however, the features of trigeminal neuropathic pain, such as hyperalgesia, allodynia, hypoesthesia, and hypoalgesia, might precede secondary trigeminal neuralgia.[2]

To our knowledge, the results of a quantitative sensory testing (QST) protocol for the assessment of trigeminal neuropathic pain due to a brain tumor have not been reported to date. Herein, we report the case of trigeminal neuropathic pain that might predict secondary trigeminal neuralgia.

  Case Report Top

  Patient presentation Top

A 48-year-old female presented with a chief complaint of paroxysmal pain in the left mandible and numbness of the lower lip and tongue and “wrenching” and “cutting” pain in the left tongue. The pain intensity was moderate with occasional exacerbations of severe headache from the left temporal to the mandibular region, lasting 1–2 min.

The initial onset of the patient's chief complaints was 1 year and 8 months ago, when she became aware of numbness on the left part of the tongue and lower lip. Six months later, she developed severe paroxysmal pain in the lower lip on the left side when drinking cold water; however, the pain resolved spontaneously. One month before presenting at our clinic, the patient developed paroxysmal pain in the entire lower jaw and temporal region on the left side, lasting 1–2 min, while washing the face, touching the cheeks, eating, and facing downwards. Numbness persisted since its initial onset but remained confined to the lower lip and tongue on the left side.

Examination of the temporomandibular joint revealed an active range of motion of >40 mm and tenderness in the left masseter muscle. Cranial nerve examination revealed slight sensory loss to light touch in the lower lip and tongue on the left side.

A panoramic radiograph showed radiolucent areas at the apices of the mandibular left second premolar and maxillary left second premolar and second molar [Figure 1]; however, provocation testing of these teeth did not reproduce the familiar pain.
Figure 1: Panoramic radiograph shows radiolucent areas at the apices of the mandibular left second premolar and maxillary left second premolar and second molar

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Quantitative sensory testing

The QST protocol of the German Research Network on Neuropathic Pain was followed.[3] The values were abnormal for the cold pain threshold (CPT = 25.8°C), heat pain threshold (HPT = 40.3°C), and mechanical detection threshold (MDT = 1.0 mN). The MDT value indicated a loss of function, whereas the CPT and HPT values indicated a gain of function.[3]

Magnetic resonance imaging findings

Magnetic resonance imaging scans revealed a well-defined, intensely enhanced 23 mm × 10 mm mass in the left cerebellopontine angle [Figure 2]a, compressing the left trigeminal nerve, which was equal in signal to the cerebrospinal fluid [Figure 2]b, [Figure 2]c, [Figure 2]d. The radiological diagnosis was an epidermoid tumor. Although the first line of treatment for trigeminal neuralgia is carbamazepine,[4] the patient was prescribed mirogabalin (Tarlige®) (2.5 mg/day) due to allergies. She experienced some relief 3 days later; however, she discontinued the treatment due to dizziness and drowsiness. The patient was referred to a neurosurgeon who excised the tumor under general anesthesia. The facial pain disappeared immediately thereafter; however, partial numbness in the tongue and lips persisted.
Figure 2: Magnetic resonance imaging revealed a well-defined, intensely enhanced mass in the left cerebellopontine angle (a), compressing the left trigeminal nerve (b and c). The pons was slightly compressed by the mass (d), which extended from near the centre of the pontine tank on the rostral side to the left side of the medulla oblongata on the caudal side

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Histopathological report

The specimen was a cystic lesion backed by a nonthinned flat epithelium, and the content was mainly a stalk. The histopathological diagnosis was an epidermoid tumor.

  Discussion Top

Secondary trigeminal neuralgia is diagnosed when there are the symptoms of classical trigeminal neuralgia, including paroxysmal pain, caused by underlying diseases, such as space-occupying lesions.[5] Based on the anatomical findings, Kitahara et al. classified the relationships between tumors (acoustic nerve tumor, meningioma, and epithelioid tumor) and the trigeminal nerve and cerebral blood vessels into three groups.[2],[6] In the Type 1 relationship, the tumor compresses a blood vessel that compresses the root entry zone of the trigeminal nerve, causing trigeminal neuralgia. In the Type 2 relationship, the tumor compresses the trigeminal nerve that is compressed by the artery opposite to the tumor (commonly the superior cerebellar artery), causing trigeminal neuralgia. The Type 3 relationship has three subgroups, in which the tumor directly compresses the trigeminal nerve, causing trigeminal neuralgia.

In this case, the anatomical relationship was Type 3, with the tumor directly compressing the trigeminal nerve root. Cerebrovascular vessels, such as the superior cerebellar artery and the anterior inferior cerebellar artery, were not involved in the compression of the trigeminal nerve root. Our patient exhibited cold and heat hyperalgesia and mechanical hyposensitivity in the mandibular region on the affected side. The cold threshold is mediated by Aδ and C-fibers, whereas the heat threshold is mediated by C-fibers. The patient complained of severe recent pain when drinking cold water, which was likely a clinical manifestation of cold hyperalgesia.

Svensson et al. developed a simple neurosensory testing that can be used by the general dentist.[7] It can be performed as follows: A metal spatula is cooled in a refrigerator until it is 5°C or heated in a water bath until it is 40°C and then applied to the affected area and contralateral unaffected area to test for the differences in the temperature sensitivity. A cotton swab is applied to the affected area and the contralateral unaffected area to assess for differences in the detection of light pressure.

Temporomandibular disorders (TMDs) are the most common type of nonodontogenic pain. The diagnosis is often elusive, as it requires a comprehensive assessment.[8] In this case, the entire left mandible was affected during severe pain, which required distinguishing it from TMD.

In cases where dentists have not arrived at a definitive diagnosis, irreversible treatment should be avoided and various diagnostic techniques should be explored.[8],[9],[10]

  Conclusion Top

Trigeminal neuropathic pain might precede secondary trigeminal neuralgia. When patients with sensory impairment visit a general practitioner, such as a dentist, the clinical features should be identified and simple neurosensory testing should be performed to differentiate between the two.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Baad-Hansen L, Eliav E, Imamura Y. International classification of orofacial pain, 1st edition (ICOP). Cephalalgia 2020;40:192-200.  Back to cited text no. 1
Noma N, Hayashi M, Kitahara I, Young A, Yamamoto M, Watanabe K, et al. Painful trigeminal neuropathy attributed to a space-occupying lesion presenting as a toothache: A report of 4 cases. J Endod 2017;43:1201-6.  Back to cited text no. 2
Ozasa K, Nishihara C, Watanabe K, Young A, Khan J, Sim C, et al. Somatosensory profile of a patient with mixed connective tissue disease and Sjögren syndrome. J Am Dent Assoc 2020;151:145-51.  Back to cited text no. 3
Winardi AM, Himawan LS. CRC9: Management of trigeminal neuralgia in a patient after lower tooth extraction: A case report. J Indian Prosthodont Soc 2018;18 Suppl 1:S39.  Back to cited text no. 4
Khan J. Neuropathic pain. J Indian Prosthodont Soc 2016;16:114-5.  Back to cited text no. 5
[PUBMED]  [Full text]  
Kitahara I, Fukuda A, Imamura Y, Ikawa M, Yokochi T. Pathogenesis, surgical treatment, and cure for sunct syndrome. World Neurosurg 2015;84:1080-3.  Back to cited text no. 6
Svensson P, Drangsholt M, Pfau DB, List T. Neurosensory testing of orofacial pain in the dental clinic. J Am Dent Assoc 2012;143:e37-9.  Back to cited text no. 7
Quek SY, Kalladka M, Kanti V, Subramanian G. A new adjunctive tool to aid in the diagnosis of myogenous temporomandibular disorder pain originating from the masseter and temporalis muscles: Twin-block technique. J Indian Prosthodont Soc 2018;18:181-5.  Back to cited text no. 8
[PUBMED]  [Full text]  
Kalladka M, Navaneetham A, Eliav E, Khan J, Heir G, Mupparapu M. Presentation of cysticercosis of the lateral pterygoid muscle as temporomandibular disorder: A diagnostic and therapeutic challenge. J Indian Prosthodont Soc 2018;18:377-83.  Back to cited text no. 9
  [Full text]  
Kalladka M, Quek S, Heir G, Eliav E, Mupparapu M, Viswanath A. Temporomandibular joint osteoarthritis: Diagnosis and long-term conservative management: A topic review. J Indian Prosthodont Soc 2014;14:6-15.  Back to cited text no. 10


  [Figure 1], [Figure 2]


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