Abstract
Background
The lacrimal nerve supplies the lacrimal gland, the lateral upper eyelid, and a small cutaneous area adjacent to the external canthus. First division trigeminal neuralgia, supraorbital/supratrochlear neuralgia, and infraorbital neuralgia have been acknowledged as neuralgic causes of pain in the forehead and periorbit. However, the lacrimal nerve has never been identified as a source of facial pain. Here we report two cases of lacrimal neuralgia.
Case reports
A 66-year-old woman had continuous pain in the lateral aspect of her left superior eyelid and an adjacent area of the temple since age 64. A 33-year-old woman suffered from continuous pain in a small area next to the lateral canthus of her left eye since age 25. In both patients the superoexternal edge of the orbit was tender. In addition, sensory dysfunction could be demonstrated within the painful area. Anaesthetic blockades of the lacrimal nerve with lidocaine 2% resulted in complete but short-lasting relief. Pregabalin provided a complete response in the first patient. The second patient was refractory to various oral and topical drugs and different radiofrequency procedures, but she eventually obtained partial relief with pregabalin.
Conclusions
Lacrimal neuralgia should be considered among the neuralgic causes of orbital and periorbital pain.
Keywords
Introduction
Generally speaking, pain in the forehead and the orbital or periorbital area may arise from local sources of pain and neuralgias, as well as the intracranial disorders and primary headaches that commonly refer the pain to the anterior regions of the head. The ophthalmic division of the trigeminal nerve (V-1) gives rise to the terminal branches that supply sensory innervation to the forehead, the eye globe, the orbit, the superior eyelid and a small area of the temple, while the terminal branches of the maxillary division (V-2) give sensory fibres to the skin of the temple, the inferior eyelid and the cheek. Specifically, the skin around the orbit is innervated by the supraorbital (V-1), supratrochlear (V-1), infraorbital (V-2) and lacrimal (V-1) nerves (1). So far, V-1 trigeminal neuralgia (2,3), supraorbital/supratrochlear neuralgia (4–7) and infraorbital neuralgia (8,9) have all been acknowledged as neuralgic causes of pain in the forehead and periorbit (10,11). However, the lacrimal nerve has never been involved as a putative source of facial pain. The lacrimal nerve supplies the lacrimal gland, the lateral upper eyelid and a small cutaneous area adjacent to the external canthus (Figure 1). Our aim was to report the first two cases of lacrimal neuralgia.
Skin area supplied by the left lacrimal nerve (shaded area). The lacrimal nerve gives sensory innervation to the lateral upper eyelid and a small cutaneous area adjacent to the external canthus.
Case reports
Patient 1
A 66-year-old woman, with no history of trauma or any other relevant disease, started suffering from pain in the lateral aspect of her left superior eyelid and a small area of the temple just next to the lateral angle of her left eye at age 64. The patient was able to point out the painful area with well-defined boundaries. The pain was moderate to severe in intensity, and sore and burning in character. The temporal pattern was chronic and continuous since onset. She clearly noticed worsening upon lateral eye movements.
The neurological exam showed hypoesthesia in the area supplied by the left lacrimal nerve along with tenderness upon deep palpation between the eye globe and the external edge of the left orbit. Otherwise, palpation of the eyeball, the trochlear area, the temporal artery, the temporalis muscle, the temporo-mandibular joint, and the emergence and course of other pericranial nerves was completely normal. An ophthalmologic exam including funduscopy, optometry, slit lamp examination, intraocular pressure measurements, visual field testing and the Schirmer test did not reveal any abnormality.
Magnetic resonance imaging (MRI) of the orbit and the head did not show any underlying lesion. Haematological and biochemical blood tests, including erythrocyte sedimentation rate, thyroid tests and immunological screening, were also normal. The patient’s emotional state was not affected, according to the Beck Depression Inventory (BDI-II) (12) and the State-Trait Anxiety Inventory (STAI) (13). An anaesthetic blockade of the lacrimal nerve was performed by injecting 0.5 cc of lidocaine 2% with a 25-gauge needle (Figure 2). The needle was inserted through the upper eyelid along the lateral wall of the orbit, and the anaesthetic solution was injected behind the lacrimal gland at a depth of approximately 2.5 cm (14,15). This procedure provided complete but transient pain relief, lasting around four hours.
Lacrimal nerve block. The eyeball is retracted medially, and the needle is inserted slightly above the outer canthus. The needle is then advanced gradually while maintaining contact with the lateral orbit wall. The anaesthetic solution is injected approximately 2.5 cm posterior to the orbital rim.
Drug therapy with pregabalin 150 mg daily was prescribed, and the patient experienced absolute relief. Treatment was maintained for a period of nine months, with no recurrences. Four months after discontinuation the symptoms resumed with identical features, and again responded to a second therapeutic course of pregabalin.
Patient 2
A 33-year-old woman, without remarkable medical history, had been suffering from a circumscribed head pain since she was 25. The pain was localised in a small area adjacent to the lateral canthus of her left eye. It was described as moderate to severe in intensity, and pressing or stabbing in character. The temporal pattern was chronic and continuous since onset. The patient herself noticed that the symptomatic area was tender, and that light touch could be perceived as painful. In fact, she avoided putting make-up on her left upper eyelid, and sleeping on her left side. Combing her hair on the left side or chewing could occasionally trigger paroxysmal exacerbations.
The neurological exam demonstrated superficial hypoesthesia, hyperesthesia and allodynia in the area supplied by the left lacrimal nerve. The superoexternal angle of the left orbit was hypersensitive to palpation, but there were no other tender points in the pericranial structures. A thorough ophthalmologic examination and a psychiatric evaluation were entirely normal. The BDI-II (12) and STAI (13) gave average results.
Cranial and orbital MRI did not reveal any abnormality. All laboratory tests, including erythrocyte sedimentation rate, thyroid tests and immunological screening, were normal. A lumbar puncture showed an opening pressure of 14 cm of water, and the cerebrospinal fluid biochemical and cytological parameters were within normal ranges. Anaesthetic blockades of the left lacrimal nerve with lidocaine 2% (14,15) were performed on four different occasions, using the technique described above (Figure 2). Every time the nerve block resulted in complete but short-term relief lasting up to six hours.
Treatment with oral indomethacin, ibuprofen, gabapentin, flunarizine, carbamazepine, oxcarbazepine, topiramate, amitriptyline, duloxetine, mirtazapine and tramadol were all of no avail. Lidocaine patches or capsaicine cream applied in the symptomatic area were also ineffective. Pulsed radiofrequency of the lacrimal nerve, the gasserian ganglion, the sphenopalatine ganglion and the ophthalmic nerve were also carried out with the aim of reducing the pain. For these procedures an insulated needle was placed in the vicinity of the nerve or ganglion to be lesioned, and the correct position was established by testing sensory stimulation. A grounded electrode was then passed through the insulated needle to the tip, and brief pulses of high-voltage electric current were applied to the nearby neural structures (16). None of these interventions resulted in any significant improvement. Only treatment with oral pregabalin (400 mg daily) provided partial but substantial relief.
After eight years of follow-up, the pain and allodynia were still localised in the territory of the lacrimal nerve. However, the patient experienced a slight spatial widening, with some pain or discomfort beyond the original borders of the painful area. By that time two additional anaesthetic blockades were performed, and again rendered a complete but transient response.
Discussion
The lacrimal nerve is one of the three branches of the ophthalmic division of the trigeminal nerve (V-1) along with the frontal nerve – which divides into the supratrochlear and supraorbital nerves – and the nasociliary nerve (17,18). In the orbit, it runs along the upper border of the lateral rectus muscle, and finally splits into two branches (17). The lateral branch supplies the lacrimal gland, while the medial branch gives off several filaments that supply sensory innervation to the lateral aspect of the upper eyelid and the adjacent area of the temple (Figure 1). Within the lacrimal compartment, the lateral branch receives a contribution of the zygomatic nerve, which conveys the autonomic fibres for the lacrimal gland (1,17,18).
The diagnosis of pericranial neuralgias is based on the topography of the pain, which remains confined within the territory of a particular nerve of the head surface (10,11,19,20), and is confirmed by short- or long-lasting relief upon anaesthetic blockade of the nerve (21). Moreover, a local structural lesion affecting the nerve trunk has to be excluded in order to further classify a given neuralgia as primary. In our patients primary lacrimal neuralgia was well documented, according to the topography of the pain, successful blockades of the nerve and a thorough diagnostic screening without any evidence of a local, intracranial or systemic source of the pain. It is true that the lacrimal nerve enters the orbit through the narrowest part of the superior orbital fissure, and then runs close to other anatomical structures (18,22). However, contiguous structures were apparently spared in our two patients, just as occurs in other primary or idiopathic neuralgias. Nevertheless, microtrauma or other subtle disorders cannot be completely discarded as possible causes of the damage to the nerve.
Pain distribution was somewhat different in the two patients. Patient 1 had pain both in the upper eyelid and a small area of the temple, whereas Patient 2 localised her pain only in the temple. Apart from possible anatomical variations, this difference could be explained by a selective involvement of some particular nerve filaments in each patient. On the other hand, neither of our patients showed any significant changes in lacrimation. Secretomotor fibres could have been spared owing to differences in topography or differences in vulnerability in comparison with sensory fibres. In fact, they come from the pterygopalatine ganglion via the maxillary nerve (V-2) and the zygomatic nerve (a branch of V-2), and join the lateral branch of the lacrimal nerve at a very distal level, just in the lacrimal compartment (1,17,18).
In our patients, lacrimal neuralgia presented with daily and continuous pain of moderate to severe intensity, with occasional exacerbations, accompanied by local symptoms and signs of sensitive dysfunction including slight hypoesthesia. Given the presence of clinically detectable sensory changes, this clinical picture could be also termed lacrimal neuropathy. However, pain was the predominant symptom in both patients, so lacrimal neuralgia would be an appropriate term following the current diagnostic criteria of cranial neuralgias (10). In fact, such sensory changes have been reported in some other patients suffering from terminal branch neuralgias (4,5). Concerning the temporal profile, lacrimal neuralgia/neuropathy apparently behaves like other neuralgias of the terminal branches of the trigeminal nerve. It seems that pericranial or downstream neuralgias (e.g. supraorbital neuralgia) are prone to produce a chronic and continuous pain (4–7), whereas proximal or upstream neuralgias (e.g. trigeminal neuralgia) are more likely characterised by lightning-like pain attacks (23). Within the same metameric level, a lesion or dysfunction may bring about different temporal manifestations of the pain depending on whether proximal or distal segments of the nerve fibres are affected.
In Patient 1 the pain remained confined within the territory of the lacrimal nerve from the onset of symptoms to date, the follow-up period being two years. Yet, in Patient 2 the symptomatic area slightly extended beyond the innervation territory eight years after onset. It is well known that damage or dysfunction of a nerve can also cause referred pain in the territory of the same metameric level. Otherwise, an expansion of the original painful area can also be due to central sensitisation driven from a peripheral neuropathic process (24).
Lacrimal neuralgia has to be differentiated from other neuralgias affecting the orbital and periorbital area (10,11), such as supraorbital (4–7) or V-1 trigeminal neuralgia (2,3). In addition, it must be distinguished from nummular headache, which is characteristically fixed within a small round or elliptical area of the head surface (10,25–27). Persistent idiopathic facial pain must also be considered in the differential diagnosis when the symptoms seem to change and expand over time (10,28–30). In all instances a careful and dynamic assessment of the symptomatic area, along with the assessment of the response to nerve anaesthetic blockades, may lead to a precise diagnosis.
To our knowledge, these are the first reported cases of lacrimal neuralgia. The fact that the nerve trunk entirely runs inside the orbit may render it less vulnerable to external forces. This may justify why lacrimal neuralgia seems to be extremely rare. Otherwise, the diagnosis of lacrimal neuralgia may have been overlooked, and possibly mistaken for other causes of facial pain. Indeed, a possible tenderness at the emergence or the course of the lacrimal nerve cannot be easily assessed. In addition, nerve blockades of this particular nerve are not easy to perform, since the anaesthetic has to be injected intraorbitally (14,15). All these circumstances may explain why lacrimal neuralgia has not been reported before. Lacrimal neuralgia may be uncommon and difficult to diagnose. Nevertheless, it should be considered among the neuralgic causes of orbital and periorbital pain.
Clinical implications
The first two cases of lacrimal neuralgia are reported. Lacrimal neuralgia should be considered among the neuralgic causes of orbital and periorbital pain.
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.