First Case of Occipital Neuralgia Treated by Fascial Hydrodissection

Background

Occipital neuralgia is a type of neuropathic pain caused by irritation or injury of the greater occipital, lesser occipital, and third occipital nerves [1]. Given that only one epidemiologic dataset has been reported, the incidence and prevalence of occipital neuralgia are not extensively known [2]. The clinical features of occipital neuralgia include unilateral or bilateral headaches involving the greater, lesser, and third occipital nerve regions; these headaches are recurrent and paroxysmal [3]. Occipital neuralgia has a significant impact on patient quality of life owing to the great intensity and sharp stabbing nature of the pain [4]. Occipital neuralgia is also characterized by the presence of trigger points along the course of the nerve [5,6]. Patients are usually prescribed multimodal medical management for occipital neuralgia, which comprises physical therapy (such as neck rest and massage), medications (such as non-steroidal anti-inflammatory drugs, antiepileptics, and antidepressants), nerve blocks, botulinum toxin injections, pulsed radiofrequency, nerve stimulation, and surgical treatments [7,8]. One of the diagnostic criteria of occipital neuralgia proposed by the International Headache Society is temporary relief from headache following the use of a nerve block; thus, nerve blocks are used for both diagnosing and treating neuralgia [9]. The pathophysiology of occipital neuralgia is unknown [10]. In recent years, the relationship between myofascial pain syndrome and nerve compression has attracted attention in the pathophysiology of neuralgia. A technique called “hydrodissection” has been reported, wherein the surrounding structures, such as the fascia, are separated from the nerve by injecting a combination of local anesthetic and saline or 5% dextrose [11]. The mechanism of action of hydrodissection involves the release of pressure by the injected solution on the structures surrounding the nerve [11]. However, only a few case reports of successful treatment with hydrodissection are available. Accumulation of evidence is needed to evaluate the efficacy of hydrodissection for neuropathic pain. In particular, to the best of our knowledge, no study to date has reported such treatment for occipital neuralgia. Therefore, the purpose of this study was to verify the effectiveness of hydrodissection for occipital neuralgia. We report the first case of successful treatment of occipital neuralgia using ultrasound-guided hydrodissection of the fascia.

Case Report

An 81-year-old woman visited our Emergency Department (ED) with a chief concern of headache lasting 4 days. She had a history of dyslipidemia, hypertension, and overactive bladder and was using rosuvastatin 2.5 mg, olmesartan 20 mg, fesoterodine 4 mg, and bilastine 20 mg. She had no history of smoking and occasionally consumed alcohol. She had no history of substance abuse. She was unemployed at the time, lived alone, and was independent in activities of daily living. The pain was stabbing and electric shock-like in nature, and the patient rated her pain 10/10 on the numeric pain rating scale. The headache was paroxysmal, and each episode lasted approximately 1 h. The location of the headache coincided with the area innervated by the right greater and lesser occipital nerves. Head computed tomography (CT) performed on the day before her initial visit to our department revealed no abnormalities. The patient had visited the ED 3 times (3, 2, and 1 days before her initial visit) and received a diagnosis of occipital neuralgia by the physician in charge of the ED. This was treated with a nerve block by injecting 2 mL of 1% lidocaine in the area innervated by the greater and lesser occipital nerves, with the physician using the landmark method. Immediately after the injection, the pain improved from a numeric pain rating scale score of 10 to a score of approximately 3; however, severe pain recurred after a few hours. During the initial examination, the patient’s vital signs were stable, and there was no skin rash. The patient had headache in the right occipital, temporal, and parietal regions, which coincided with the dominant regions of innervation by the right greater and lesser occipital nerves, and allodynia was observed when the same areas were stimulated. Hard trigger points were palpated 1 cm caudal to the occipital ridge, 2.5 cm lateral to the midline, and 2 cm caudal to the right mastoid process, and strong, reproducible tenderness was noted. Ultrasonography revealed that the right semispinalis capitis and sternocleidomastoid muscles were present directly under each trigger point. Based on the history and physical examination, the patient’s headache was found to be in the region of the greater and lesser occipital nerves, and allodynia was observed when the same areas were stimulated. The headache was characterized by intense, recurrent, paroxysmal, and sharp pain. Tenderness was noted at the origin of the greater and lesser occipital nerves, and local anesthetic blockade of both areas provided temporary pain relief. Head CT showed no evidence of cerebral hemorrhage, cerebral infarction, subarachnoid hemorrhage, or other organic disease causing the headache. Therefore, the diagnosis of occipital neuralgia was confirmed (Table 1); however, we considered it inadequately treated. We thought that the occipital neuralgia was probably caused by occipital nerve compression due to myofascial pain. Hydrodissection was considered, as we had prior experience in treating neuralgia attributed to myofascial pain syndrome with hydrodissection [12]. Subsequently, ultrasound-guided hydrodissection of the interfascicular space between the right semispinalis capitis and obliquus capitis inferior muscles was performed with 5 mL of 0.75% ropivacaine, resulting in immediate and complete resolution of the headache in the area innervated by the right greater occipital nerve (Figure 1, Video 1). Next, ultrasound-guided hydrodissection of the deep layer of the right sternocleidomastoid muscle was performed using a low-dose anesthetic agent (a mixture of 9 mL saline and 1 mL 1% lidocaine), resulting in immediate resolution of the headache in the area innervated by the right lesser occipital nerve. Oral acetaminophen 2000 mg/day and loxoprofen 120 mg/day were prescribed for recurrent episodes. Subsequently, 2 and 6 days following her initial visit, hydrodissection of the fascia of the right semispinalis capitis and obliquus capitis inferior muscles was performed using a low-dose anesthetic agent (a mixture of 9 mL saline and 1 mL 1% lidocaine) outpatient in the Department of General Internal Medicine. In addition, 10 days after the initial examination, hydrodissection of the deep layer of the right sternocleidomastoid muscle was performed using the same low-dose anesthetic agent in the same department. From the initial visit to 10 days later, the patient’s clinical condition progressed as follows: the headache in the right lesser occipital nerve region disappeared completely, while headache in the right greater occipital nerve region, with a numeric pain rating scale score of 2, recurred every few days but was tolerable. Subsequently, the frequency of attacks decreased further, and the analgesic medication was discontinued 23 days following the initial examination. No recurrence of the headache was observed at 4 weeks following analgesic discontinuation. No adverse events due to hydrodissection occurred. Figure 2 provides a summary of our interventions.

Written informed consent was obtained from the patient for publication of this report. Ethics approval for this study was provided by the ethics committee of Rakuwakai Marutamachi Hospital, and the study was conducted in accordance with the guidelines of the Declaration of Helsinki.

Discussion

To the best of our knowledge, this was the first case of successful treatment of occipital neuralgia using ultrasound-guided hydrodissection of the fascia. The characteristic history of headache, presence of tender points on examination, and no presence of abnormalities on head CT met the diagnostic criteria for myofascial pain syndrome and occipital neuralgia (Table 1) [13]. Therefore, this case study suggests an association between myofascial pain syndrome and occipital neuralgia. The patient originally experienced severe shoulder stiffness, which may have triggered her symptoms.

In general, the greater occipital nerve runs through the muscular layer of the semispinalis capitis and obliquus capitis inferior muscles. A nerve block is performed by targeting the nerve in this region either using the landmark method or under ultra-sound guidance [14–16]. In contrast, the lesser occipital nerve is one of the terminal branches of the superficial cervical plexus in addition to the great auricular, transverse cervical, and supraclavicular nerves emerging from behind the dorsal border of the sternocleidomastoid muscle. Techniques for superficial cervical plexus block are used to target this region [17–19]. Using these techniques, hydrodissection for occipital neuralgia can be performed, as in the present case. One of the mechanisms of action of hydrodissection for nerve pain is nerve decompression [11]. In our patient’s case, the initial nerve block performed using the landmark method resulted in immediate recurrence of neuralgia upon fading of the effect of the local anesthetic, whereas the symptoms improved quickly after ultrasound-guided fascial hydrodissection with nearly no recurrence of symptoms thereafter. This clinical course provides further evidence that myofascial pain syndrome can cause neuralgia. In addition, cadaver studies have shown that even a small amount of drug injected into the interfascicular space can spread widely and penetrate deeper structures [20]. The nerve block performed using the landmark method provided temporary analgesia because the anesthetic could not completely penetrate into the interfascicular space that was compressing the nerve, whereas hydrodissection provided long-term analgesia since it was able to separate the nerve from the surrounding fascia, which allowed the anesthetic agent injected under ultrasound guidance to reach the targeted area. Since the purpose of treatment in this case was to relieve pressure on the nerve, local anesthetics were not necessary. The low-dose anesthetic agent used in this case is relatively safe with a low risk of local anesthetic poisoning since it is mostly composed of saline solution. Moreover, we can ensure that the anesthetic is injected between the fascia and avoid accidental puncture of the occipital artery, which runs near the greater occipital nerve, using ultrasound guidance [14–16]. In Japan, insurance policies do not allow sole injection of saline; hence, we mixed a small amount of lidocaine with saline to perform the hydrodissection. However, it is theoretically possible to perform hydrodissection using only saline for the treatment of myofascial pain syndrome. In this case, ropivacaine was used for the initial hydrodissection of the greater occipital nerve region. This is because the first injection provides reliable analgesia and serves the purpose of a nerve block.

This report is groundbreaking in that it presented hydrodissection as an effective new method for the treatment of occipital neuralgia. Moreover, the presented treatment can be applied to other types of neuralgia. An increasing number of reports, similar to our case study, have examined the role of the fascia in myofascial pain syndrome. Thus, fascial hydrodissection should be considered in suspected cases of nerve pain due to myofascial pain syndrome [21–24].

A possible limitation of this case report is the short follow-up period. Since occipital neuralgia could recur even following treatment, a longer follow-up period assessing the long-term efficacy of fascial hydrodissection is warranted [25,26].

Conclusions

Fascial hydrodissection is a useful treatment method for occipital neuralgia caused by myofascial pain syndrome. Hydrodissection is a relatively safe procedure with a low risk of local anesthetic poisoning, given that saline or a low-dose anesthetic agent is considered adequate as the injection solution. Fascial hydrodissection is recommended as a new treatment for occipital neuralgia. Treatment with hydrodissection may be applicable to other neuralgia types.