The maxillofacial region is complex in its anatomy and in its variation in the presentation of neurologic disorders. The diagnosis and management of neurologic disorders in clinical practice remains a challenge. A good understanding of the neurologic disorder in its entirety helps dentists in the diagnosis and appropriate referral to a specialist for further investigations and management of the condition. Neurologic disorders described in this article are under broad categories of sensory and motor disturbances as well as movement disorders and infections. This article summarizes the most common maxillofacial neurologic disorders that dentists might encounter in clinical practice.
Key points
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Sensory disturbances of the maxillofacial region include trigeminal neuralgia, glossopharyngeal neuralgia, persistent idiopathic facial pain, burning mouth syndrome, cluster headache, geniculate neuralgia, and temporal arteritis.
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Motor disturbances that are of importance to dentists include Bell palsy, multiple sclerosis, central poststroke pain, syringobulbia, and Tourette syndrome and their association with maxillofacial structures and their management or referral when encountered in dental practice.
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Movement disorders such as cerebral palsy and Parkinson disease, and their maxillofacial manifestations.
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Infections such as neurosyphilis, leprosy, and herpes zoster are discussed with a focus on maxillofacial structures.
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Where possible, imaging of the head and neck region with special focus on magnetic resonance neurography is discussed, with pertinent image sequences.
Introduction
Diagnosis and management of patients with neurologic disorder in clinical practice remain a challenge to all dentists. A good understanding of the neurologic disorder in all its aspects, including its clinical presentation, examination findings, relevant investigations, and prior management, help clinicians identify the condition when presented as a comorbidity alongside the dental conditions. Once identified or suspected, the patient can be referred for further multidisciplinary work-up and management. This article describes sensory, motor disturbances, and movement disorders of neurologic origin that may be encountered in routine dental practice ( Box 1 ) and conditions likely to be seen by dental practitioners in which the initial presenting symptoms could be facial pain, numbness, tingling, or discomfort.
- A.
Sensory disturbances
- 1.
Trigeminal neuralgia
- 2.
Trigeminal anesthesia dolorosa
- 3.
Glossopharyngeal neuralgia
- 4.
Persistent idiopathic facial pain
- 5.
Burning mouth syndrome
- 6.
Cluster headache
- 7.
Nervus intermedius neuralgia (geniculate neuralgia)
- 8.
Migraine
- 1.
- B.
Motor disturbances
- 1.
Bell palsy
- 2.
Multiple sclerosis
- 3.
Central poststroke pain
- 4.
Syringobulbia
- 5.
Tourette syndrome
- 1.
- C.
Movement disorders
- 1.
Cerebral palsy
- 2.
Parkinson disease
- 1.
- D.
Infections
- 1.
Lepromatous neuropathy
- 2.
Herpes Zoster
- 3.
Neurosyphilis
- 1.
Sensory disturbances
Trigeminal Neuralgia (Tic Douloureux)
Definition
According to the International Classification of Headache Disorders, Third Edition (ICHD-3), trigeminal neuralgia, also called tic douloureux, is characterized by sudden onset of recurrent unilateral electric shock–like, stabbing, or shooting pain lasting between a fraction of a second and 2 minutes.
It occurs along the distribution of the trigeminal nerve and has a trigger zone/point, typically in the maxillary (V2) and maxillary (V3) nerve distributions.
Pain is triggered by innocuous stimuli such as facial touch, brushing teeth, talking, or cold air. However, patients have intermittently pain-free periods, with pain occurring sporadically and terminating abruptly. Symptoms occur in the absence of neurologic deficits.
Types of trigeminal neuralgia
- 1.
Classic trigeminal neuralgia
- a.
Idiopathic form: no disorder is evident.
- b.
Classic form: hypothesized to be related to vascular compression on the trigeminal nerve near the skull base or vasospasm.
- a.
- 2.
Secondary (symptomatic) trigeminal neuralgia: occurs from presence of brain tumors, infections, multiple sclerosis, trauma, and so forth. Most commonly, prior dental procedures or anesthetic injections can cause such iatrogenic injuries.
Epidemiology
Most cases of trigeminal neuralgia occur in women more than 40 years of age, peaking between 50 and 60 years. An incidence of 4.3 to 32.1 per 100,000 person years and prevalence of 0.07% to 0.3% has been reported.
Clinical presentation
Unilateral sharp, shooting, electric shock–like, paroxysmal or episodic pain symptoms are commonly encountered. Pain is severe enough for the patient to stop any ongoing activity, including cessation of talking midsentence.
In addition to patients with paroxysmal pain, there is another group of patients with trigeminal neuralgia that present with constant burning pain, usually affecting 1 side of the face. It is important to consider this subtype and recognize such atypical presentations, in order not to miss a diagnosis of trigeminal neuralgia.
Diagnosis is based on thorough history and clinical examination ( Boxes 2 and 3 ).
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Pain from trigeminal neuralgia must have the following characteristics:
- 1.
Lasts from a fraction of a second to 2 minutes
- 2.
Sudden onset and termination
- 3.
Paroxysmal
- 4.
Electric shock–like, stabbing, or shooting pain
- 5.
Severe intensity
- 6.
Precipitated by an innocuous stimulus within the affected trigeminal nerve distribution
- 7.
No neurologic deficits
- 1.
-
Diagnosis:
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Thorough history taking
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Cranial nerve examination
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MRI
- •
-
Pretreatment work-up
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Electrocardiogram
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Complete blood count
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Complete metabolic panel
- •
-
Management
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Pharmacologic:
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Carbamazepine: first-line treatment
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Oxcarbazepine
- •
Baclofen
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Gabapentin
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Pregabalin
- •
Lamotrigine
- •
-
Surgical:
- •
Microvascular decompression
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Stereotactic (Gamma knife) therapy
- •
Balloon decompression
- •
Glycerol blockade
- •
Radiofrequency thermoregulation
- •
Investigations
Imaging
Imaging techniques include MRI/magnetic resonance (MR) angiography (MRA)/MR neurography (MRN). Brain MRI is important at the time of diagnosis to differentiate between classic and secondary trigeminal neuralgia. MRI detects lesions such as nerve sheath tumor, compressive vascular disorders, and abnormal enhancement with neuritis.
Electrocardiography is especially important to detect the presence of an atrioventricular (AV) block, because carbamazepine and oxcarbazepine (discussed later) are contraindicated in patients with AV block. More recently, MRN has been used to identify the neurologic abnormalities because the three-dimensional (3D) imaging protocols using MRN have evolved with excellent vascular signal suppression. Trigeminal neuralgia can be diagnosed using MRN ( Fig. 1 ). The affected nerve s show increased T2 signal and/or thickening on MRN. MRN aids in identification of neuropathy, confirms the clinical suspicion, and can guide focused treatments, such as rhizotomy. MRN aids in detecting the site of neuropathy, injury, or perineural fibrosis. It is also helpful in grading the nerve injury for future neurolysis or nerve repair procedures ( Figs. 2 and 3 ).
Laboratory studies
- 1.
Complete metabolic panel, including electrolyte levels, liver function, and renal function, should be assessed before starting the patient on pharmacologic management.
- 2.
Complete blood count (CBC): used in monitoring cell counts during treatment with carbamazepine.
Management
Pharmacologic
Sodium channel blockers are the first-line drugs in the management of patients with trigeminal neuralgia. Both carbamazepine and oxcarbazepine are highly effective, with mechanism of action being the blockade of voltage-gated sodium channels.
Patients on carbamazepine require periodic CBC assessment, because this drug is known to cause aplastic anemia in 1% to 2% of users. Oxcarbazepine is better tolerated than carbamazepine and with fewer side effects.
For patients with allergies or drug interactions with carbamazepine, or who have low sodium levels, baclofen or lamotrigine are other beneficial alternatives.
Neuromodulation therapy
This technique is explored for the treatment of chronic neuropathic pain. Although certain types of peripheral nerve stimulation procedures are US Food and Drug Administration (FDA) approved for pain in the extremities and back, using this technique for facial pain is still considered an off-label use ( Fig. 4 ).
Surgical
- 1.
Microvascular decompression is a common surgical procedure if the condition is nonresponsive to medication
- 2.
Glycerol blockade
- 3.
Radiofrequency thermocoagulation
- 4.
Stereotactic (Gamma Knife) radiosurgery
Trigeminal anesthesia dolorosa
Trigeminal anesthesia dolorosa is a chronic central neuropathic pain characterized by severe and debilitating deafferentation pain. It is an uncommon complication after surgical or traumatic injury to the trigeminal nerve. Although rare, it has been reported in patients who underwent trigeminal rhizotomy, a procedure in which heating current is used to destroy nerve fibers sending pain signals to the brain.
Clinical features, investigation, and management
Constant burning or aching pain is noted along the distribution of the affected trigeminal nerve, despite numbness in the area. MRN can show abnormalities of the peripheral trigeminal nerve and/or its branches, confirming the clinical symptoms. This condition is empirically managed by either gabapentin or surgery.
Glossopharyngeal Neuralgia
Definition
Glossopharyngeal neuralgia is an uncommon condition, with pain located in the oropharyngeal area: pharynx, posterior third of tongue, soft palate, ear, and inferior border of mandible. In addition, patients occasionally present with bradycardia, syncope, or asystole. Pain presents just like in trigeminal neuralgia and is triggered by swallowing, yawning, or talking.
Epidemiology
There is an incidence of 0.2 to 0.8 per 100,00 population per year, with onset noted mostly in patients more than 50 years of age. An equal male to female ratio is reported.
Clinical presentation
Characteristic symptoms of sharp shooting pain in the oropharynx and inner part of the lower mandible aids diagnosis. A thorough history and clinical examination is therefore beneficial.
Types of glossopharyngeal neuralgia
- 1.
Classic glossopharyngeal neuralgia: can be idiopathic or from vascular compression of glossopharyngeal nerve.
- 2.
Secondary glossopharyngeal neuralgia: secondary to trauma, tumor, surgery, or irradiation of the oropharynx.
Investigations
Laboratory
- 1.
Erythrocyte sedimentation rate (ESR)
- 2.
CBC
- 3.
Complete metabolic panel
- 4.
Antinuclear antibody
Imaging
Techniques include MRI, MRA, and MRN. MRI and MRA are used to exclude an organic lesion. MRN aids in direct visualization of neural lesions.
Treatment
Pharmacologic treatment is similar to treatment of trigeminal neuralgia.
Glossopharyngeal nerve block with local anesthesia, with or without the addition of steroids, can be used as an adjunct to pharmacologic management.
Surgical
Treatment modalities are similar to treatment of trigeminal neuralgia. In addition, rhizotomy is an effective surgical treatment option.
Persistent Idiopathic Facial Pain
Persistent idiopathic facial pain (PIFP) is also known as atypical odontalgia, phantom facial pain, and atypical facial pain. According to ICDH-3, PIFP is defined as constant facial and/or oral pain with varying presentations, occurring for at least 2 h/d, and lasting for more than 3 months. Diagnosis is established when the patient presents with the symptoms listed earlier, and with no clinical neurologic deficit. It is unrelated to burning pain in the tongue or oral mucosa, as discussed later in relation to burning mouth syndrome (BMS).
Epidemiology
PIFP is a rare condition with an incidence of 4.4 per 100,000 years and prevalence of 0.03%.
Eighty percent of patients with this condition attribute onset of symptoms to a dental treatment.
Clinical presentation
Patients describe an aching, throbbing, or burning type of pain. Pain is poorly localized, deep, and usually unilateral, with no evident disorder on the routine imaging studies.
There is an association between the onset of symptoms and a previous dental treatment.
Investigation
Diagnosis might involve an inferior alveolar nerve block or local infiltration with local anesthetic agent. However, patients sometimes have an equivocal response to this maneuver, with occasional complete resolution of pain and, at other times, pain persisting.
Imaging
Panoramic or periapical radiographs are used to rule out an odontogenic source of pain. MRN is being increasingly used for such patients. It is common to see entrapment neuropathy or evidence of prior peripheral trigeminal nerve injury, aiding in clarifying the cause in many such cases.
Management
Pharmacologic
Use of low-dose antiseizure medications (eg, gabapentin or tricyclic antidepressants) has proved effective in patient management. Topical medications such as capsaicin have also shown some efficacy.
Other treatments
Some patients report benefit with low-level laser treatment or behavioral management. Other forms of management with few evidence-based studies include trigeminal ganglion blocks, high-frequency repetitive transcranial magnetic stimulation, and hypnosis. Use of computed tomography (CT)–guided injection and pulsed radiofrequency treatment of sphenopalatine ganglion has been reported in a small number of refractory cases ( Fig. 5 ).
Burning Mouth Syndrome
Definition
BMS presents as an unexplained pain, dysesthesia, or burning in a clinically normal and healthy oral mucosa. A diagnosis is established if the symptoms discussed earlier recur daily for more than 2 h/d and for at least 3 months as per the definition from the Committee of the International Headache Society. It is a diagnosis of exclusion, and other systemic, local medical or dental sources of pain must be ruled out.
Epidemiology
The disorder is more common among postmenopausal middle-aged-women, with a male to female ratio of 1:5 to 1:7 and prevalence of 1%.
Although the cause is unknown, some associated factors, such as stress, hormonal dysfunction, parafunctional habits, anxiety, depression, psychiatric disorders, and neuropathy, might play a role in the syndrome onset and/or excerbation.
Clinical presentation
Patients with BMS describe a spontaneous onset of continuous scalding, rawness, and annoying burning pain. Sensation can vary in intensity during the day, and usually occurs bilaterally. The most common site is the tip of tongue, but it can present on other oral mucosal surfaces.
Some patients report a temporary relief of symptom with food in the mouth, whereas some report aggravation with spicy and acidic foods or alcohol.
Investigation
There is no investigation diagnostic for BMS; however, the following tests can help rule out other systemic or local causes of oral burning:
- 1.
Gram stain and culture to rule out candidiasis.
- 2.
CBC, folate, ferritin, iron, B 12 to exclude anemia or nutritional deficiency.
- 3.
Salivary flow test to rule out xerostomia.
There are also no positive findings on imaging.
Management
Patients with this condition occasionally present with cancer phobia and typically have been to multiple providers before the diagnosis is established.
The first step in managing these patients is to reassure them that there is no association with cancer and the condition can be managed with conservative means.
Topical or systemic pharmacologic agents have been used successfully to manage or distract some patients with BMS. These agents include alpha lipoic acid, low-dose clonazepam, which should be discontinued with caution as a result of associated withdrawal syndrome (suicidal tendencies); topical capsaicin; gabapentin; amitriptyline; and doxepin. Other treatment strategies used are low-level laser therapy, stress, and behavioral management.
Cluster Headache
Definition
Cluster headache (CH) is classified as a trigeminal autonomic cephalgia by the International Headache Society. This form of headache comes in clusters occurring at about the same time each day for a few weeks to several months, after which patients experience pain-free periods.
CHs can be chronic or episodic and have a serious impact on quality of life and the patient’s productivity. Patients also have suicidal thoughts and typically present with anxiety and/or depression.
Epidemiology
CH is most common in young men, with a prevalence of 0.1%. The age of onset is, on average, 30 years, with clusters commonly noted in the spring weather.
Risk factors include alcohol and nitroglycerine intake.
Clinical presentation
The pain onset is sudden and often severe, and presents unilaterally in the temporal/periorbital area, with about 1 to 8 attacks occurring daily or every other day. Each attack lasts from 15 minutes to 3 hours. The patients also present with the following symptoms on the affected side: tearing in eyes, nasal congestion, runny nose, edema of eyelids, drooping eyelids, and bloodshot eyes.
Investigation
Imaging studies
MRI or MRA to rule out brain/pituitary mass. MRN may be used to evaluate supraorbital or occipital nerves. Distention and tortuosity of optic nerve sheaths may be seen in ocular hypertension or intracranial increased pressure.
Laboratory
Calcitonin gene–related peptide (CGRP) is being evaluated as a potential biomarker for CH, although its sensitivity and specificity are yet to be established.
Risk factors include alcohol and nitroglycerine intake.
Management
The first thing to consider in the management of patients with CH is to prevent acute attacks by preventing triggers, such as tobacco and alcohol, and daily use of pharmacologic agents such as verapamil, topiramate, short-term corticosteroids, and lithium. Triptans are very effective in the treatment of acute episodes of CH, especially when administered subcutaneously or intranasally. One-hundred percent oxygen and sublingual ergotamine have also been used successfully in managing the acute pain. Fremanezumab and galcanezumab are monoclonal CGRP antibodies currently being considered as investigational drugs in the treatment of CH.
Nervus Intermedius Neuralgia (Geniculate Neuralgia)
Nervus intermedius neuralgia is an extremely rare neuralgia arising from the sensory fibers of nervus intermedius, a branch of the facial nerve. It supplies the pinna, external auditory meatus, and retroauricular area. ICH-3 defines nervus intermedius neuralgia as paroxysmal pain episodes presenting deep in the ear and lasting a few seconds to minutes.
There are 2 types of nervus intermedius neuralgia:
- 1.
Classic
- 2.
Secondary
Although there is no specific underlying cause of the classic type, the secondary type is seen after herpes zoster infection (Ramsay Hunt syndrome) involving the nervus intermedius.
Clinical presentation
The classic type presents as recurrent paroxysmal unilateral stabbing, shooting, or sharp pain deep to the auditory canal. It can be triggered by a mechanical or sensory stimulus, with occasional radiation to the parieto-occipital area.
In the secondary type, in addition to the features in classic nervus intermedius neuralgia, the patients further present with ipsilateral facial paralysis and signs of herpetic eruptions on/in the ear on the affected side.
Investigations
On MRI or MRN, the nerve may show thickening, T2 hyperintensity, and enhancement of the facial nerve and its branches.
Management
Management is similar to trigeminal neuralgia.
Migraine
Definition
Migraine is a type of primary headache. It is recurrent and patients usually experience at least 5 episodes before the diagnosis is established. Each episode lasts between 2 hours and 72 hours.
There are 2 subtypes of migraine:
- 1.
Migraine with aura: patients present with neurologic symptoms that are focal and transient. This aura occurs either before or concurrent with the headache. The most prevalent aura is visual aura, with patients experiencing light flashes and photophobia. Other forms of aura include motor weakness and speech disturbance.
- 2.
Migraine without aura: no specific neurologic symptoms that give the patient a premonition of an incipient migraine attack.
Like CH, it presents with autonomic symptoms. The difference between the two conditions is that migraines present with bilateral autonomic features. Recently, new hypothesis of neural compressions has been proposed for migraine attacks: supraorbital or supratrochlear nerve involvement in frontal headaches and occipital nerve compression by posterior skull base muscles in the occipital neuralgia. These conditions have been shown to produce pain improvement with anesthetic and botulinum toxin injections at the trigger points, somewhat validating this hypothesis.
Epidemiology
Migraine is the third most prevalent condition and the seventh leading cause of disability worldwide. It is more common in women, with an incidence of 14.1 to 18.9 per 1000 years and a prevalence of 17% to 33%. A positive family history is present in 26% of cases.
Clinical presentation
The patients present with a sudden onset of unilateral moderate to severe throbbing or pulsating pain in the frontotemporal area. In children and teenagers, the symptoms can be bilateral. Patients may also present with light and sound sensitivity, nausea, and vomiting.
Investigation
The diagnosis is usually clinical. MRN may be performed in doubtful cases or with nonspecific symptoms. Imaging may show abnormal T2 hyperintensity and/or thickening of the greater or lesser occipital nerves ( Fig. 6 ).
