Boris Filipović

Behavioral and immunohistochemical evidence for central antinociceptive activity of botulinum toxin A

Botulinum toxin A (BTX-A) is approved for treatment of different cholinergic hyperactivity disorders, and, recently, migraine headache. Although suggested to act only locally, novel observations demonstrated bilateral reduction of pain after unilateral toxin injection, and proposed retrograde axonal transport, presumably in sensory neurons. However, up to now, axonal transport of BTX-A from periphery to CNS was identified only in motoneurons, but with unknown significance. We assessed the effects of low doses of BTX-A injected into the rat whisker pad (3.5 U/kg) or into the sensory trigeminal ganglion (1 U/kg) on formalin-induced facial pain. Axonal transport was prevented by colchicine injection into the trigeminal ganglion (5 mM, 2 μl). To find the possible site of action of axonally transported BTX-A, we employed immunohistochemical labeling of BTX-A-truncated synaptosomal-associated protein 25 (SNAP-25) in medullary dorsal horn of trigeminal nucleus caudalis after toxin injection into the whisker pad. Both peripheral and intraganglionic BTX-A reduce phase II of formalin-induced pain. Antinociceptive effect of BTX-A was prevented completely by colchicine. BTX-A-truncated SNAP-25 in medullary dorsal horn (spinal trigeminal nucleus) was evident 3 days following the peripheral treatment, even with low dose applied (3.5 U/kg). Presented data provide the first evidence that axonal transport of BTX-A, obligatory for its antinociceptive effects, occurs via sensory neurons and is directed to sensory nociceptive nuclei in the CNS.

Central action of peripherally applied botulinum toxin type A on pain and dural protein extravasation in rat model of trigeminal neuropathy.

Background Infraorbital nerve constriction (IoNC) is an experimental model of trigeminal neuropathy. We investigated if IoNC is accompanied by dural extravasation and if botulinum toxin type A (BoNT/A) can reduce pain and dural extravasation in this model. Methodology/Principal Findings Rats which developed mechanical allodynia 14 days after the IoNC were injected with BoNT/A (3.5 U/kg) into vibrissal pad. Allodynia was tested by von Frey filaments and dural extravasation was measured as colorimetric absorbance of Evans blue - plasma protein complexes. Presence of dural extravasation was also examined in orofacial formalin-induced pain. Unilateral IoNC, as well as formalin injection, produced bilateral dural extravasation. Single unilateral BoNT/A injection bilaterally reduced IoNC induced dural extravasation, as well as allodynia (lasting more than 2 weeks). Similarly, BoNT/A reduced formalin-induced pain and dural extravasation. Effects of BoNT/A on pain and dural extravasation in IoNC model were dependent on axonal transport through sensory neurons, as evidenced by colchicine injections (5 mM, 2 µl) into the trigeminal ganglion completely preventing BoNT/A effects. Conclusions/Significance Two different types of pain, IoNC and formalin, are accompanied by dural extravasation. The lasting effect of a unilateral injection of BoNT/A in experimental animals suggests that BoNT/A might have a long-term beneficial effect in craniofacial pain associated with dural neurogenic inflammation. Bilateral effects of BoNT/A and dependence on retrograde axonal transport suggest a central site of its action.

Activity of botulinum toxin type A in cranial dura: implications for treatment of migraine and other headaches

Although botulinum toxin type A (BoNT/A) is approved for chronic migraine treatment, its mechanism of action is still unknown. Dural neurogenic inflammation (DNI) commonly used to investigate migraine pathophysiology can be evoked by trigeminal pain. Here, we investigated the reactivity of cranial dura to trigeminal pain and the mechanism of BoNT/A action on DNI.

Botulinum toxin type A activity in cranial dura: implications for treatment of migraine and other headaches

Although botulinum toxin type A (BoNT/A) is approved for chronic migraine treatment, its mechanism of action is still unknown. Dural neurogenic inflammation (DNI) commonly used to investigate migraine pathophysiology can be evoked by trigeminal pain. Here, we investigated the reactivity of cranial dura to trigeminal pain and the mechanism of BoNT/A action on DNI.

Dural neurogenic inflammation induced by neuropathic pain is specific to cranial region

Up to now, dural neurogenic inflammation (DNI) has been studied primarily as a part of migraine pain pathophysiology. A recent study from our laboratory demonstrated the occurrence of DNI in response to peripheral trigeminal nerve injury. In this report, we characterize the occurrence of DNI after different peripheral nerve injuries in and outside of the trigeminal region. We have used the infraorbital nerve constriction injury model (IoNC) as a model of trigeminal neuropathic pain. Greater occipital nerve constriction injury (GoNC), partial transection of the sciatic nerve (ScNT) and sciatic nerve constriction injury (SCI) were employed to characterize the occurrence of DNI in response to nerve injury outside of the trigeminal region. DNI was measured as colorimetric absorbance of Evans blue plasma protein complexes. In addition, cellular inflammatory response in dural tissue was histologically examined in IoNC and SCI models. In comparison to the strong DNI evoked by IoNC, a smaller but significant DNI has been observed following the GoNC. However, DNI has not been observed either in cranial or in lumbar dura following ScNT and SCI. Histological evidence has demonstrated a dural proinflammatory cell infiltration in the IoNC model, which is in contrast to the SCI model. Inflammatory cell types (lymphocytes, plasma cells, and monocytes) have indicated the presence of sterile cellular inflammatory response in the IoNC model. To our knowledge, this is the first observation that the DNI evoked by peripheral neuropathic pain is specific to the trigeminal area and the adjacent occipital area. DNI after peripheral nerve injury consists of both plasma protein extravasation and proinflammatory cell infiltration.

Lasting reduction of postsurgical hyperalgesia after single injection of botulinum toxin type A in rat

A single injection of low doses of botulinum toxin type A (3.5 U/kg) completely abolished secondary mechanical hyperalgesia throughout its duration in a model of post surgical pain after gastrocnemius incision in rat.

Treatment of Frontal Secondary Headache Attributed to Supratrochlear and Supraorbital Nerve Entrapment With Oral Medication or Botulinum Toxin Type A vs Endoscopic Decompression Surgery

Importance Endoscopic surgical decompression of the supratrochlear nerve (STN) and supraorbital nerve (SON) is a new treatment for patients with frontal chronic headache who are refractory to standard treatment options. Objective To evaluate and compare treatment outcomes of oral medication, botulinum toxin type A (BoNT/A) injections, and endoscopic decompression surgery in frontal secondary headache attributed to STN and supraorbital SON entrapment. Design, Setting, and Participants Prospective cohort study of 22 patients from a single institution (Diakonessen Hospital Utrecht) with frontal headache of moderate-to-severe intensity (visual analog scale [VAS] score, 7-10), frontally located, experienced more than 15 days per month, and described as pressure or tension that intensifies with pressure on the area of STN and SON. A screening algorithm was used that included examination, questionnaire, computed tomography of the sinus, injections of local anesthetic, and BoNT/A in the corrugator muscle. Interventions Different oral medication therapy for headache encountered in the study cohort, as well as BoNT/A injections (15 IU) into the corrugator muscle. Surgical procedures were performed by a single surgeon using an endoscopic surgical approach to release the supraorbital ridge periosteum and to bluntly dissect the glabellar muscle group. Main Outcomes and Measures Headache VAS intensity after oral medication and BoNT/A injections. Additionally, early postoperative follow-up consisted of a daily headache questionnaire that was evaluated after 1 year. Results In total, 22 patients (mean [SD] age, 42.0 [15.3] years; 7 men and 15 women) were included in this cohort study. Oral medication therapy reduced the headache intensity significantly (mean [standard error of the mean {SEM}] VAS score, 6.45 [0.20] [95% CI, 0.34-3.02; P < .001] compared with mean [SEM] pretreatment VAS score, 8.13 [0.22]). Botulinum toxin type A decreased the mean (SEM) headache intensity VAS scores significantly as well (pretreatment, 8.1 [0.22] vs posttreatment, 2.9 [0.42]; 95% CI, 3.89-6.56; P < .001). The mean (SEM) pretreatment headache intensity VAS score (8.10 [0.22]) decreased significantly after surgery at 3 months (1.30 [0.55]; 95% CI, 5.48-8.16; P < .001) and 12 months (1.09 [0.50]; 95% CI, 5.71-8.38; P < .001). There was a significant decrease of headache intensity VAS score in the surgical group over the BoNT/A group (mean [SEM] VAS score, 2.90 [0.42]) after 3 months (mean [SEM] VAS score, 1.30 [0.55]; 95% CI, 0.25-2.93; P < .001) and 12 months (mean [SEM] VAS score, 1.09 [0.50]; 95% CI, 0.48-3.16; P < .001) after surgery. Conclusions and Relevance Endoscopic decompression surgery had a long-lasting successful outcome in this type of frontal secondary headache. Even though BoNT/A had a positive effect, the effect of surgery was significantly higher. Level of Evidence 3.

Decompression endoscopic surgery for frontal secondary headache attributed to supraorbital and supratrochlear nerve entrapment: a comprehensive review

In the last decade, a new surgical treatment modality was developed for frontal secondary headache, based on the assumption that the trigger of this pain entity is the entrapment of peripheral sensory nerves. The surgery entails a procedure, where an endoscopic approach is used to decompress the supraorbital and supratrochlear nerve branches, which are entrapped by the periosteum in the region of the corrugator supercilii muscle. Candidates for the surgery define their headache as moderate to severe persistent daily pressure or tension, localized in the frontal area, sometimes accompanied by symptoms of nausea and photophobia mimicking a primary headache—migraine. We created a step-by-step screening algorithm which is used to differentiate patients that have the highest chance for a successful surgical decompression. Up to now, published data regarding this type of surgery demonstrate long-lasting successful outcomes while adverse effects are minor. This article reviews and discusses from a surgeon’s perspective decompression surgery for secondary headache attributed to supraorbital and supratrochlear nerve entrapment.

Axonal transport of botulinum toxin A from periphery to CNS in sensory and motor nerves

Background: Botulinum toxin A (BTX-A) has been approved for treatment of movement disorders and migraine. The widely assumed peripheral mechanism of action has been questioned by recent studies which demonstrated an axonal transport in the facial nerve and within central nerves. Findings in our laboratory suggested a central antinociceptive activity following axonal transport in the sciatic nerve. Methods: To characterize the axonal transport of BTX-A, the toxin’s enzymatic activity in the CNS was assessed using immunofluorescent detection of its cleaved substrate synaptosomal-associated protein 25(SNAP-25) following injections into the rat whisker pad and hind-paw, intramuscular injection into the gastrocnemius and intraneural injections into the sciatic nerve. Intraneural and intraganglionic colchicine was employed to block axonal transport. To investigate the significance ofaxonal transport for antinociceptive activity of BTX-A, we assessed the effect of peripheral and intraganglionic injections of low dose BTX-A in orofacial formalin-induced pain in rats. Results: Following whisker pad BTX-A injection, cleaved SNAP-25 was observed in the dorsal horn of the medulla. Cleaved SNAP-25 following subcutaneous, intramuscular and intraneural toxin injection in rat hind limbs was observed in corresponding segments of ipsilateral dorsal and ventral horn. Central SNAP-25 cleavage following BTX-A injection into the sciatic nerve was prevented by colchicine. In the ventral horn, BTX-A protease was localized within cholinergic neurons. Facial and intraganglionic injections of BTX-A prevented orofacial pain dependent on axonal transport in the trigeminal sensory nerve. Conclusions: Our results suggest that the axonal transport of BTX-A in different sensory and motor nerves commonly occurs after peripheral administration. Axonal transport in sensory neurons followed by central enzymatic activity is involved in botulinum toxin’s antinociceptive effects. The possible functional role of axonal transport in motor neurons remains to be examined. Acknowledgements: The antibody to cleaved SNAP-25 was a kind gift from Ornella Rossetto (University of Padua, Italy). The study was funded by the Croatian Ministry of Science, Education and Sport and theDeutscher Akademischer Austausch Dienst.