الفهرس 
Pathophysiological Consideration in the HeadacheOnly 14 pages are availabe for public view
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Abstract
Headache can occur as a result of activation of pain sensitive cranial structures, such as the dura mater, vasculature, and the cranial and cervical muscles and ligaments, which are innervated by primary afferent neurons originating from the trigeminal and dorsal root ganglia of the upper cervical spinal nerves. In relation to nociception in cases of headache, two types of nerve fiber are considered to be important: the smallcaliber, unmyelinated, slow-conducting fibers called C fibers, and the small-diameter, lightly myelinated, more rapid-conducting fibers called Ad fibers. Findings from nerve stimulation studies indicate that C fibers transmit aching, throbbing, or burning pain that builds up slowly, whereas the Ad fibers conduct sharper initial pain sensation.
Headache after general anesthesia has been reported to range from 10% up to 38% during the first 24 hours. When patients are monitored for the occurrence of headache during the first week after surgery, this number increases to 48%. However, the incidence of chronic daily headache in the general population ranges from 5% to 30%; thus a portion of patients, had they not had surgery, would have been prone for the development of a headache anyway.
The perioperative period is stressful, and tension and stress related headaches may be exacerbated during this time. A significant percentage of the population consumes caffeine containing drinks on a regular basis, and the perioperative period often limits caffeine intake.
Caffeine causes cerebral vasoconstriction and withdrawal probably causes rebound vasodilatation which results in the development of headache.
Strong correlation between the occurrence of postoperative headache after general anaesthesia and:
• Duration of preoperative fasting.
• Use of atracurium and tracheal intubation.
• Use of nitrous oxide in patients with inflamed sinuses or air-containing middle-ear spaces.
• Hypercapnia.
• Cardiac transplantation.
• Increased intracranial pressure.
• Many drugs can cause vascular headaches by inducing vasodilation.
• Drug-induced aseptic meningitis.
• Pregnancy-induced hypertension and eclampsia.
• Postpartum period.
Headache that develops less than seven days after a spinal puncture, occurs or worsens less than fifteen minutes after assuming the upright position, and improves less than thirty minutes in the recumbent position with at least one of the following (neck stiffness, tinnitus, photophobia, and nausea). The headache should disappear within fourteen days after a spinal puncture; if it persists, it is called a CSF fistula Headache.
The pathophysiology of PLPH is still unclear, it is thought to develop as a result of leakage of CSF through the dural puncture. Continuous leakage of CSF leads to decreased CSF pressure and volume,the loss of CSF volume activates adenosine receptors, which leads to vasodilatation and headache.
PDPH is probably a vascular type headache and epidural blood patch relieves the headache by its vaso-constrictive action. This cerebral vasoconstriction may be caused by subarachnoid spread of the injected blood. The possible role that the rich innervations of the dura matter with adrenergic, cholinergic, and peptidergic fibers may play a role in PDPH.
Headache is a common and potentially disabling disorder. Under certain circumstances of pattern, frequency, severity, and other factors, the disorder may qualify for a diagnosis of a primary headache. Under other circumstances, headache may reflect an underlying illness or condition (i.e., a secondary headache). Differentiating between primary and secondary headache is the first and most critical step in the diagnostic process.
Non -steroidal anti -inflammatory drugs (including aspirin), Paracetamol, and ibuprofen are inexpensive and widely available over the counter therapies, making them a good option for first line treatment.
A combination of paracetamol 1,000 mg, aspirin 1,000 mg and caffeine 260 mg may be more effective (84% pain relief at two hours) than aspirin 500 mg or sumatriptan 50 mg alone for patients with mild to moderate migraine.
Ketoprofen 75-150 mg also provided relief to 62% of patients with migraine at two hours.
Aspirin has a high response rate for relief of pain at two hours in patients with episodic tension-type headache (75% for 1,000 mg, and 70% for 500mg p=0.011). Paracetamol 1,000 mg had a similar rate (71%).
Caffeine is a cerebral vasoconstrictor and one study has demonstrated a reduction of cerebral blood flow after intravenous administration of caffeine sodium benzoate for PDPH.Caffeine is also a potent CNS stimulant.
Hydrocortisone was effective to treat PDPH after failed conservative measures and EBP. Hydrocortisone for Adenosine diphosphate (ADP) patients may be useful because it is a noninvasive technique and the incidence and severity of PDPH in this group of patients is high. Controlled studies are needed to determine the actual role of hydrocortisone in preventing and treating PDPH.