From the Guidelines
Diagnosing trigeminal neuralgia primarily relies on a thorough clinical history and physical examination, with the most recent and highest quality study suggesting the use of MRI with contrast to exclude structural causes like tumors or vascular compression of the trigeminal nerve 1. The diagnosis is made when a patient reports characteristic brief, severe, electric shock-like pain attacks in one or more branches of the trigeminal nerve distribution (typically affecting the cheek, jaw, teeth, gums, or lips), usually triggered by light touch, eating, talking, brushing teeth, or exposure to cold air. These attacks typically last seconds to minutes, with pain-free intervals between episodes.
Key Diagnostic Steps
- Physical examination is often normal, but may reveal trigger zones where light touch provokes pain.
- Neurological examination should be performed to rule out other conditions, focusing on cranial nerve function, especially trigeminal nerve sensory and motor components.
- Magnetic resonance imaging (MRI) with contrast is recommended to exclude structural causes like tumors or vascular compression of the trigeminal nerve.
- In some cases, MRI with specialized sequences (FIESTA or CISS) may be needed to visualize the trigeminal nerve and potential vascular compression.
- Laboratory tests are not diagnostic but may help rule out other conditions.
- The response to carbamazepine (starting at 100mg twice daily and gradually increasing) can be both therapeutic and diagnostic, as dramatic pain relief strongly supports the diagnosis.
Differential Diagnoses
- Dental pathology
- Temporomandibular joint disorders
- Multiple sclerosis
- Other facial pain syndromes These should be excluded through appropriate testing, as suggested by the most recent study 1.
Imaging Techniques
- MRI head allows for direct visualization and excellent assessment of the brainstem and intracranial course of CN V.
- MRI orbits, face, and neck can be used to evaluate the entire extracranial course of the nerve.
- 3-D heavily T2-weighted MRI sequences, MRA, and a combination of these techniques can be used to characterize the anatomy of vascular loops potentially compressing the fifth nerve, as reported in the latest study 1.
From the Research
Diagnosis of Trigeminal Neuralgia
- Trigeminal neuralgia is characterized by touch-evoked unilateral brief shock-like paroxysmal pain in one or more divisions of the trigeminal nerve 2.
- The diagnosis of trigeminal neuralgia is clinical, but high-quality imaging is mandatory to identify secondary causes and a neurovascular contact 3.
- MR imaging, including high-resolution trigeminal sequences, should be performed as part of the diagnostic work-up 4.
- New methods such as DTI (diffusion tensor imaging) allow a more differentiated assessment of the consequences of a vascular contact on the trigeminal nerve 3.
Diagnostic Criteria
- Trigeminal neuralgia can be subclassified into classical TN (CTN) and secondary TN (STN) 2.
- New diagnostic criteria, which subclassify TN on the basis of presence of trigeminal neurovascular conflict or an underlying neurological disorder, should be used as they allow better characterization of patients and help in decision-making regarding medical and surgical treatments 4.
Differential Diagnosis
- Important differential diagnoses include trigeminal autonomic cephalalgias, posttraumatic or postherpetic pain and other facial pains 2.
- A thorough clinical evaluation is necessary to rule out other conditions that may mimic trigeminal neuralgia 5.
Role of Imaging
- Imaging studies, such as MRI, can help identify secondary causes of trigeminal neuralgia, such as multiple sclerosis or a space-occupying lesion affecting the trigeminal nerve 2, 3.
- High-resolution trigeminal sequences can help identify neurovascular conflict, which is a common cause of classical trigeminal neuralgia 4, 3.