Abstract
Introduction
The infratrochlear nerve supplies the medial aspect of the upper eyelid, the superolateral aspect of the nose and the lacrimal caruncle. This nerve may contribute to the pain stemming from the trochlea, but infratrochlear neuralgia has not been identified as a specific cause of pain.
Methods
Over a 10-year period we have been recruiting patients with pain in the internal angle of the orbit that did not show features of trochlear pain.
Results
Seven patients (six female, one male; mean age, 46.1 ± 18.9) presented with pain in the territory of the infratrochlear nerve. The pain appeared in the internal angle of the orbit and upper eyelid (n = 3), the superolateral aspect of the nose (n = 3), or the lacrimal caruncle (n = 1). All patients had a paroxysmal pain, with the attacks lasting five to 30 seconds. Pain attacks were mostly spontaneous, but two patients had triggers. Between attacks, all patients had local allodynia. Pain did not increase with vertical eye movements. Six patients were treated with gabapentin with complete response, and one patient experienced long-lasting relief with an anesthetic blockade of the infratrochlear nerve.
Conclusion
Infratrochlear neuralgia should be considered as a possible cause of pain in the internal angle of the orbit.
Keywords
Introduction
Pain in the internal angle of the orbit is frequently attributed to a trochlear source, either primary or secondary (1–5). Trochlear headache (trochleodynia) is a periorbital or frontal pain that is typically associated with tenderness of the trochlea and exacerbation with vertical ductions. Trochleodynia should be differentiated from other disorders producing pain in the territory supplied by the first division of the trigeminal nerve (V-1) with a median or paramedian topography. Within such a clinical frame the differential diagnostic possibilities are limited, and mainly consist of supraorbital/supratrochlear neuralgia (6–9), nasociliary neuralgia (10–13), idiopathic rhinalgia (14), “trochlear migraine” (15) and “nasal migraine” (16). All such disorders arise from different sources of pain, either peripherally or centrally.
Trochleodynia originates in the superior oblique muscle-tendon-trochlea complex, the pain being conveyed by intraorbital branches of the ophthalmic division of the trigeminal nerve (V-1), including the infratrochlear nerve. The infratrochlear nerve stems from the nasociliary nerve (one of the terminal branches of V-1) and follows its same direction along the inferior edge of the superior oblique muscle up to its pulley (17,18). It exits the orbit inferior to the trochlea and supplies the medial aspect of the upper eyelid and the bridge of the nose as well as the lacrimal sac and caruncle. Whether the somatic and neuropathic components of trochlear pain could be differentiated was a challenge. We have observed that dysfunction of the infratrochlear nerve gives rise to a distinctive neuralgia that can be differentiated clinically from trochleodynia and other disorders producing pain in the internal angle of the orbit. We believe that such an observation carries important diagnostic and therapeutic implications. Herein, we report the first seven cases of infratrochlear neuralgia.
Patients and methods
Over a 10-year period we have been recruiting patients with pain restricted to the internal angle of the orbit that did not show the features of trochlear pain. Exclusion criteria included concomitant chronic headache and/or cervical painful conditions, systemic painful disorders, previous surgical procedures or trauma to the head, face, eyes, nose or neck, eyeglass or contact lens wearing, history of chronic sinusitis, history of psychiatric disorders and involvement in litigation.
A thorough physical and neurological exam was performed in all patients. Physical assessment always included palpation of the eyeball, the trochlear area, and the nasal bones as well as the emergence and course of the supraorbital, supratrochlear, and infraorbital nerves. Depending on the topography of the pain, the patients were also examined by an ophthalmologist or an ear, nose and throat (ENT) surgeon. Ophthalmological exam included funduscopy, optometry, slit lamp examination, intraocular pressure measurements, testing of visual fields and the Schirmer test. ENT exam always included rhinoscopy. Moreover, the psychological status of all adult patients was assessed with the Beck Depression Inventory (BDI-II) (19) and the State-Trait Anxiety Inventory (STAI) (20).
Supplementary examinations consisted of routine biochemistry and hematology tests, including erythrocyte sedimentation rate, C-reactive protein and thyroid tests; immunological tests, including quantitative immunoglobulin testing, tests for rheumatoid factor and lupus anticoagulant, as well as tests for antinuclear, anticardiolipin and antithyroid antibodies; and neuroimaging studies with magnetic resonance imaging (MRI) of the brain, the orbit and the paranasal sinuses.
Results
Demographic and clinical features of patients with infratrochlear neuralgia.
Visual analog scale, 0–10 (0: no pain; 10: the worst pain imaginable). bEstimates based on patient recall.
F: female; L: left; M: male; R: right.
All patients had a paroxysmal, shot-like pain. Pain quality was described as stabbing (n = 3), electric (n = 3) or pressing (n = 1), and pain intensity was always graded as severe (7–8 on a 10-point scale). In each patient, the pain appeared in one of three different locations within the territory supplied by the infratrochlear nerve (Figure 1): internal angle of the orbit and upper eyelid (n = 3), side of the bridge of the nose (n = 3) and lacrimal caruncle (n = 1). The symptomatic area remained fixed with time in all cases. None of the patients had conjunctival injection, lacrimation, nasal congestion, rhinorrhea or other autonomic symptoms. Pain attacks were very brief, with durations of five to 30 seconds as estimated by the patients. The paroxysms were mostly spontaneous, but two patients had attacks triggered by touch on the affected area. Six patients had the pain on a daily basis, with the frequency ranging from one to 20 attacks per day, while one patient had one to two attacks per week. The attacks were randomly distributed throughout the daytime, but did not occur during the night. Between attacks, all patients had local allodynia.
Territories of pain in infratrochlear neuralgia: (a) internal angle of the orbit and upper eyelid, (b) superolateral aspect of the nose, (c) lacrimal caruncle.
Neurological exams were normal, but the internal angle of the orbit and/or the superolateral aspect of the nose were painful upon palpation. None of the patients noted an increase of the pain with vertical eye movements. Beck and STAI scores and the results of blood tests and neuroimaging were all normal. Ophthalmological and ENT examinations of patients with either pain in the eye or pain in the nose were also normal.
Analgesics (paracetamol, metamizol) and nonsteroidal anti-inflammatory drugs (naproxen, ibuprofen, dexketoprofen, indomethacin) were tried in all cases without benefit. Specifically, all patients were on indomethacin for at least three days to no avail. Yet, gabapentin was used as a preventive in six patients, with complete response (Table 1). Drug treatment with gabapentin was discontinued after two to six months, and there were no relapses during a follow-up between eight months and four years. The last patient underwent an anesthetic blockade of the infratrochlear nerve. The nerve was blocked by injecting 0.5 cc of bupivacaine 0.5% with a 30-gauge needle through the internal angle of the orbit, just below the trochlear area (Figure 2). This procedure resulted in immediate and complete pain relief, and remission was maintained during a two-month follow-up.
Infratrochlear nerve block: The needle is inserted through the internal angle of the orbit, just below the trochlear area; the anesthetic solution is injected at the emergence of the infratrochlear nerve.
Discussion
In our patients, primary infratrochlear neuralgia was documented in accordance with the temporal and spatial characteristics of the pain, and a thorough diagnostic screening that ruled out any local, intracranial or systemic source. The diagnosis of pericranial neuralgias is essentially based on the topography of the pain, which remains confined within the territory of a particular nerve of the head surface. Infratrochlear neuralgia presented with lancinating, shot-like pain paroxysms with three distinctive locations within the territory of the infratrochlear nerve: 1) internal angle of the orbit and upper eyelid; 2) side of the bridge of the nose, and 3) lacrimal caruncle (Figure 1). Moreover, there seemed to be a clear clinico-anatomical correlation as such particular topographies respectively match with the territories supplied by the terminal branches of the infratrochlear nerve (11): 1) palpebral branch, for the medial half of the upper eyelid; 2) nasal branch, for the upper side of the nose, as well as the medial part of the conjunctiva; and 3) lacrimal branch, for the lacrimal sac and caruncle. Infratrochlear neuralgia seems to differ from other terminal branch neuralgias not only in the topography, but also in the temporal profile. All our patients described a paroxysmal pain lasting just a few seconds, according to their own estimations, while patients with supraorbital/supratrochlear, infraorbital or lacrimal neuralgia normally exhibit a continuous pain (6–9,21,22).
The diagnosis of pericranial neuralgias is confirmed by short- or long-lasting relief upon anesthetic blockade of the nerve (6–9,21,22). Diagnostic nerve blocks were not performed in six out of seven patients, given the intermittent and paroxysmal nature of their pain and their prompt response to neuromodulators. Yet, an anesthetic block of the infratrochlear nerve provided long-term relief to the last patient, thus confirming the presence of infratrochlear neuralgia.
Unlike first-branch (V-1) trigeminal neuralgia, the pain of infratrochlear neuralgia was moderate to intense but not excruciating. Additionally, the paroxysms were mostly spontaneous while trigeminal neuralgia is typically triggered by innocuous stimuli. Moreover, the pain was located in conspicuous areas within the territory of the infratrochlear nerve, whereas the pain of V-1 neuralgia develops in much wider areas within the forehead and the anterior scalp (23). Both the paucity of triggers and the lack of autonomic features differentiate infratrochlear neuralgia from short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) or short-lasting unilateral neuralgiform headache attacks with cranial autonomic symptoms (SUNA) (24,25).
Paroxysmal pain perceived in the internal angle of the eye brings to mind ophthalmodynia periodica, the first description of what is now officially named primary stabbing headache. Ophthalmodynia periodica was described by Lansche in 1964 as recurrent paroxysms of stabbing ocular pain (26). Overall, primary stabbing headache presents with transient and localized stabs of pain in the head, the temporal and fronto-ocular areas being the most frequently affected. Pain location shows a great variability both inter- and intra-individually. The majority of patients experience multifocal attacks, with the pain moving from one area to another in either the same or the opposite hemicranium. With time, patients with unifocal symptoms may also display a scattering of stabs. This lack of topographic stereotype in primary stabbing headache is at variance with neuralgias, including infratrochlear neuralgia. Moreover, primary stabbing headache and infratrochlear neuralgia differ in regards to the duration of attacks. The vast majority of primary stabbing headache paroxysms lasted from a fraction of one second to three seconds (27–31). Finally, allodynia is present in patients with infratrochlear neuralgia, and has not been described in isolated primary stabbing headache.
The distinction between infratrochlear neuralgia and idiopathic rhinalgia should not pose any problem (14). Idiopathic rhinalgia presents with continuous pain with a median distribution, either in the bridge of the nose or in the whole nose, whereas infratrochlear neuralgia emerges as a paroxysmal unilateral pain.
Migraine attacks may be localized in the face (32,33), particularly on one side of the nose (16). In such cases, the pain involves the whole side of the nose (from the bridge to the tip), the clinical features and the response to treatment being typical of migraine.
Infratrochlear neuralgia may have been occasionally regarded as trochleodynia (1–5). In fact, both disorders may produce pain and tenderness in the internal angle of the orbit, probably because of the intimate anatomic relationship between the infratrochlear nerve and the trochlear apparatus. Still, trochlear pain commonly extends to the anterior part of the ipsilateral hemicranium while infratrochlear neuralgia remains circumscribed to the territory supplied by the infratrochlear nerve. In addition, trochlear pain is typically continuous while infratrochlear neuralgia causes a paroxysmal pain. Moreover, trochlear pain is characteristically aggravated by eye movements, and this is not a feature of infratrochlear neuralgia. Trochlear injection of corticosteroids has been found to be an effective treatment for trochleodynia, but has not been tried in infratrochlear neuralgia. Instead, infratrochlear neuralgia has been treated with neuromodulators (gabapentin) with excellent response.
Infratrochlear neuralgia could be included among the painful cranial neuropathies, although its pathophysiology has not been determined. Mechanical factors might play a role in these apparently primary cases, as has been described in other pericranial neuralgias (6,34). Within the orbit, the infratrochlear nerve runs along the inferior edge of the superior oblique muscle, close to the internal wall of the orbit and nearby vessels (17,18). These anatomical particularities may facilitate subtle intermittent nerve trauma during ocular movements that would produce stretching, angulation, traction and/or friction of the nerve.
To our knowledge, these are the first reported cases of infratrochlear neuralgia. The diagnosis of infratrochlear neuralgia may have been overlooked, and possibly mistaken for other causes of orbital pain, mostly trochleodynia. This report brings forward the clinical basis for distinguishing both disorders, thus providing patients with a differential effective treatment. With the description of infratrochlear neuralgia, the clinical spectrum of pain in the internal angle of the orbit seems to have been completed.
Clinical implications
The first seven cases of infratrochlear neuralgia are reported. Infratrochlear neuralgia should be considered as a possible cause of pain at the internal angle of the orbit.
Footnotes
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Conflict of interest
None declared.