A craniotomy is a neurosurgical technique, whereby part of the skull is opened or removed for access to treat conditions such as brain tumors, aneurysms, and arterio-venous malformations. Post-craniotomy headaches (PCH) are one of the most frequently encountered adverse events after craniotomy, appearing in over two-thirds of patients undergoing the procedure. PCH fall under the category of secondary headaches and can present unique challenges in diagnosis and management. This article gives a brief overview of the current literature regarding this headache subtype.
There are many hypotheses of which can contribute to the pain response following craniotomy. One of the more straightforward mechanisms is the direct trauma from the surgery itself to the soft tissue, musculature, bone, or meninges. Other potential causes include nerve injury, debris from drilling bone irritating the internal structures and meninges, adherence of muscle to the dura mater, formation of neuroma in the surgical scar, central sensitization, and aberrant nerve regeneration.
Risk factors for PCH may include age, gender, and previous history of headaches have been disputed and remain in question. However, neurosurgical duration of greater than 4 hours has been associated with a higher prevalence of PCH. Some studies suggest that incidence increases with certain surgical approaches, for example, craniectomies have a higher incidence than craniotomies or cranioplasties, and suboccipital approach have a higher incidence than translabyrinthine approach.
Although psychiatric disorders are not risk factors for PCH, the presence of uncontrolled anxiety or depression may increase intensity and frequency of PCH, while worsening quality of life.
Unfortunately, due to methodological differences, inconsistencies in definition, and multiple surgical approaches, retrospective reviews found an incidence range that varied from zero to 100%. However, looking broadly, a majority of those studies report that greater than 30% of craniotomy patients suffered from PCH.
Chronic PCH, which is commonly seen with excision of acoustic neuromas, has an incidence of 28.4% at 3 years postoperatively.
A true description of PCH has been scant and perhaps nonspecific, but some research suggests that on history, patients may report a continuous, pulsatile or pounding pain of variable intensity that appears within seven days of the surgery. Other common characteristics include symptoms on the same side as the surgical incision and improvement of symptoms over time.
As with all headaches, it is imperative to rule out red flag signs including but not limited to paralysis, papilledema, drowsiness, confusion, memory impairment, loss of consciousness, focal neurologic signs, neck stiffness, sudden onset excruciating pain, and/or personality changes.
Some evidence points to scar neuromas as a potential trigger for headaches. Thus, it is important to assess the scar site on physical exam and evaluate for reproduction of headache pain with palpation.
PCH is primarily diagnosed through history and physical examination. However, imaging may be warranted if intracranial pathology is suspected or red flags are found on examination. If so, a non-contrast head CT scan would be an appropriate first step.
The current criteria for diagnosis according to the International Classification of Headache Disorders 3 Beta edition is as follows:
A. Any a headache fulfilling criteria C and D
B. Surgical craniotomy has been performed
C. A headache is reported to have developed within 7 days after one of the following:
D. Either of the following:
E. Not properly accounted for by another ICHD-3 diagnosis.
Of note, persistent headache attributed to craniotomy differs from the acute headache criteria by the fact that it persists for more than 3 months after the craniotomy. About a quarter of patients who develop an acute headache attributed to craniotomy go on to experience a persistent headache attributed to craniotomy. When a headache following craniotomy becomes persistent, the possibility of a medication-overuse headache should be considered.
Unfortunately, research remains lacking in regards to current strategies to manage PCH. Therefore, options for consideration include the use of typical medications seen in the treatment of headaches with similar phenotypes. A list of these medications is beyond the scope of this review, but, in the neurological population, care must be taken when using medications that may obscure the ability to monitor neurologic responses.
This is of particular importance when opioids are prescribed. They remain a heavily relied upon option for moderate to severe pain, even with the risk of addiction, cognitive clouding, and respiratory depression. Worth noting is the ability to combine other analgesics with opioids to lessen the chance of adverse events. Some combinations in past studies include fentanyl and ketorolac or tramadol and diclofenac.
Regarding prophylaxis, one single center, randomized, the blinded trial found that a preoperative dose of 100 mg of diclofenac decreased the intensity of a headache on postoperative day 1, and up to post-op day 5 for patients with infratentorial surgeries. Still, caution must be exercised due to the potential to increase the risk of bleeding with the use of non-steroidal anti-inflammatory medications.
Other interventions have been studied, either for PCH or post-craniotomy pain in general, but warrant more research before standardizing their use in these patients. These include transcutaneous electrical acupuncture stimulation, nerve blocks, gabapentinoids, COX inhibitors, and dexmedetomidine, a presynaptic alpha two adrenoceptor antagonist.
In the chronic phase, a shift to more non-pharmacological adjuncts may be considered. Alternatives to consider are physical therapy, acupuncture, TENS units, hot or cold packs, massage, or bio-behavioral interventions. A small case series of four patients demonstrated a benefit with the use of Botulinum toxin-A to treat delayed onset PCH, but similar to the other approaches; more research is needed.