15.1 Introduction

Tension-type headache or TTH is the most common form of headache. It is sometimes referred to as “stress headache” or “muscle tension headache.” There are two classifications of TTH: episodic tension-type headache (ETTH), which occurs randomly and infrequently, and chronic tension-type headache (CTTH), which occurs daily or continuously on at least 15 days per month, although the intensity of the pain may vary during a 24-hour cycle. ¹ It is estimated that 30 to 80% of the adult population in the United States suffer from occasional TTH, yet only 3% suffer from CTTH. ²

Symptoms of TTH include a tight feeling in head or neck muscles or a tightening band-like sensation around the neck or head, which creates a “vise-like” ache. The pain is typically found in the forehead, temples, or the back of the head or neck. However, there is frequently significant crossover between the symptoms of TTH and migraine without aura. In fact, in the Spectrum study, 71% of the participants initially diagnosed with episodic TTH subsequently had their diagnosis changed to migraine or migrainous headache after their headache diary was reviewed by the investigators. ³ However, the hallmark feature of TTH is increased pericranial tenderness. The third edition of the International Classification of Headache Disorders (ICHD-III) subdivides TTH into four divisions: infrequent episodic, frequent episodic, chronic, and probable; see Table 15‑1 and Table 15‑2. ⁴

The new fourth category of “probable” TTH was created due to the difficulty differentiating between TTH and migraine without aura. The etiology of TTH is thought to be related to cervical myofascial activity involving the neck, face, and scalp, which likely reflects a complex syndrome involving peripheral nociceptors in ETTH and central dysnociception in CTTH. ¹

Nonpharmacologic treatments such as relaxation and electromyography (EMG) biofeedback therapies, cognitive behavioral interventions, and various physical therapy techniques have shown various degrees of success at reducing the frequency and severity of TTH. Medications used to treat chronic daily headache include simple analgesics, such as aspirin and paracetamol, and nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen sodium. The addition of caffeine increases the efficacy of these medications. Prophylactic medications such as tricyclic antidepressants, selective serotonin reuptake inhibitors (SSRIs), the antispasmodic drug tizanidine, and topiramate may provide additional relief for some patients. Unfortunately, current pharmacotherapy for CTTH can be limited by either incomplete efficacy or intolerable side effects.

Given its effects on nociception and muscle contraction, botulinum neurotoxin (BoNT) appears to be an attractive agent in the prophylaxis of TTH. In addition to its well-known effects in reducing muscle contractions, it may also block the release of pain mediators such as substance P, glutamate, and calcitonin gene-related peptide. ⁵ Our experience with temporomandibular disorder (TMD) patients with TTH shows a 70% response rate (where a response is a 50% or greater reduction in intensity or frequency of headache) in an open-label study. Early, nonrandomized series provided encouraging data supporting the role of prophylactic treatment with BoNT-A. ⁶ The results of the PREEMPT (Phase 3 REsearch Evaluating Migraine Prophylaxis Therapy) trials 1 and 2 strongly supported the use of BoNT-A for chronic migraine prophylaxis. ^{7 ,​ 8} Given the significant crossover between the symptoms of TTH and migraine, a plausible mechanism for BoNT-A prophylaxis of TTH was established. In contrast, the results of more recent, randomized, controlled trials in 2004 for the efficacy of BoNT in the prophylactic treatment of TTH are negative. ^{9 ,​ 10} Meta-analysis in 2012 likewise revealed no association with reduction in number of TTH. ^{11 ,​ 12} However, those findings do not rule out a possible role of BoNT-A in patients with severe, unremitting forms of CTTH, especially those like the following:

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  Patients who have failed to respond adequately to conventional treatments.

  
  
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  Patients with unacceptable side effects from existing treatment.

  
  
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  Patients in whom standard preventive treatments are contraindicated.

  
  
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  Patients who are misusing, overusing, or abusing medications.

  
  
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  Patients with spasm or trigger points involving the jaw or head.