PREVALENCE BY HEADACHE TYPE

CLINICAL CLUES AND CLINICAL RULES: PRIMARY VS SECONDARY HEADACHE * Based on a presentation by David W. Dodick, MD ABSTRACT Headache is a common condition, accounting for many specialist office visits annually. International Headache Society classification and diagnostic guidelines are invaluable tools for evaluating the headache patient. These guidelines can be enhanced with clinical clues that aid in determining whether a particular headache is primary or secondary. The secondary causes of pain must be ruled out; some neurological imaging techniques and other investigations have proved more helpful than others in this regard. Fortunately, the vast majority of headaches encountered will be of the primary type. Clinicians often have difficulty distinguishing between the types of primary headache disorders, which is crucial when considering treatment options. (Adv Stud Med. 2003;3(6C):S550-S555) The emphasis in current training programs is on differentiating migraine from secondary headache, or, more precisely, identifying the symptoms of headache disorders. Clinicians, therefore, usually can distinguish primary from secondary headache but are not as adept at characterizing the different types of *Based on a presentation given by Dr Dodick at the 14th Migraine Trust International Symposium. Associate Professor of Neurology, Department of Neurology, Mayo Clinic, Scottsdale, Arizona. Address correspondence to: David Dodick, MD, Department of Neurology, Mayo Clinic Scottsdale, 13400 East Shea Boulevard, Scottsdale, AZ 85259. E-mail: dodick.david@mayo.edu. primary headache. Unfortunately, this leads to some inaccuracy and misdiagnoses of the headache disorders most frequently encountered in clinical practice. A systematic approach incorporating International Headache Society (IHS) diagnostic and classification guidelines and clinical clues beyond these guidelines will help clinicians to distinguish primary from secondary headache and differentiate types of primary headache disorders. PREVALENCE BY HEADACHE TYPE As a starting point in diagnosis, it is helpful to be aware of prevalence rates for primary and secondary headache. Overall, more than 90% of the headache patients examined annually suffer from the primary headache disorders migraine, tension-type, or cluster headache. The remaining patients have headache secondary to tumor, meningitis, giant cell arteritis, sinusitis, or other medical conditions. The difficulty is that there are more than 300 causes of secondary headache, and the IHS criteria do not address all of them. Intracranial pathology is extremely uncommon among patients with primary headache disorders. One large meta-analysis revealed that only 0.18% of patients with migraine and a normal neurological examination will have a significant intracranial abnormality. 1 In addition, a population-based study of the lifetime prevalence of headache found that tension-type headache is the most common primary headache, affecting 78% of patients, followed by migraine in 16%. Among secondary headache patients, the most common causes were fasting (19%), nasal or sinus disorders (15%), head trauma (4%), and nonvascular intracranial disease, including tumor (0.5%). 2 Several studies have focused on the prevalence of migraine and S550 Vol. 3 (6C) June 2003

migrainous headache; the estimated incidence of these headaches among men and women in the United States is shown in Figure 1. 3 A study of 3799 patients seen at a 24-hour emergency headache clinic demonstrated that 86% had primary headache and, of those, 61% received a diagnosis of migraine. Only 6.4% of all patients presented with secondary headache; sinusitis was the most common cause (1.7%), followed by posttraumatic headache (1.5%), cerebral spinal fluid leak (0.5%), and vascular disorders (0.5%). 4 These data indicate that patients presenting with severe headache are most likely to have migraine or another primary headache disorder; the likelihood of a secondary headache presenting as an emergency is quite low. disorders. The guidelines also serve as the basis for designing headache research and epidemiologic studies. These guidelines are currently undergoing revision; the new classification and diagnostic guidelines will provide more specific descriptions of the various headache disorders, including migraine with and without aura, chronic migraine, tension-type and chronic Figure 1. Prevalence of Migraine and Migrainous Headache ACCURATE DIAGNOSIS Accurate diagnosis of primary headache and migraine is important because migraine is a common condition. Also, according to US population based data, more than 90% of patients with migraine have some degree of impaired function, with 53% reporting severe impairment or requiring bed rest and 39% reporting some impairment. 5 More than 75% of patients with migraine report severe to extremely severe pain with attacks. 6 Furthermore, only 48% of patients with migraine have received a diagnosis from a physician, 40% are taking a prescription medication for migraine, and 58% are taking over-the-counter remedies only. 5 Misdiagnoses are also common. In one analysis, 48% of patients who received a diagnosis of sinusrelated headache actually had migraine, and 33% of those with a diagnosis of tension-type headache had migraine. 6 Lastly, among patients with primary headache, 70% meet IHS criteria for migraine, 23% meet IHS criteria for tension-type headache, and 7% meet IHS criteria for migrainous headache. 7 DIAGNOSTIC GUIDELINES In 1988, the IHS initiated and published the first headache classification system that was accepted worldwide. 8 These diagnostic and classification guidelines allow for a precise diagnosis of headache disorders not available for most other neurological Adapted with permission from Lipton et al. 3 Table 1.Worrisome Features SNOOP Consultation for a particular headache Systemic symptoms/signs (fever, myalgias, weight loss) Systemic disease (malignancy, acquired immune deficiency syndrome) Neurologic symptoms or signs Onset sudden (thunderclap headache) Onset after age 40 years Pattern change Progressive headache with loss of headache-free periods Change in type of headache Advanced Studies in Medicine S551

tension-type headache, and cluster headache. An expanded consideration of the secondary causes of headache will also be included. IHS guidelines referred to here are based on the proposed revisions to the original document. EXCLUDING SECONDARY HEADACHE The first step in headache diagnosis is to exclude a secondary cause. A consultation for a particular headache should include history and examination, evaluation of clinical clues and features, and a determination of whether worrisome features require further investigation. Most often, secondary headache can be suspected when 1 or more of the features shown in Table 1 are present. When a symptom indicative of secondary headache is present, a number of diagnostic tests may be considered. Electroencephalography (EEG) to exclude a structural abnormality is not useful in the routine evaluation of headache patients. However, EEG may be a useful tool in patients with headache and alteration of consciousness, encephalopathy, focal neurological deficits, or atypical aura symptoms. 9 The role of computed tomography (CT) or magnetic resonance imaging (MRI) in evaluating nonmigraine headache is unclear, and some secondary headache causes may not be evident with CT. In recurrent migraine, neither CT nor MRI is warranted unless there has been a recent change in headache pattern, new-onset seizures, or focal neurological signs or symptoms. 10,11 Indications for gadolinium-enhanced MRI include an index of suspicion for cerebrovascular processes such as arterial dissection, cerebral venous sinus thrombosis, or central nervous system vasculitis. Suspected arterial dissection should be investigated with magnetic resonance angiography and cerebral venous sinus thrombosis should be investigated with magnetic resonance venography. Other indications for gadolinium-enhanced MRI include suspicion of herpes encephalitis; high and low intracranial pressure syndromes; and tumors of the posterior fossa, pituitary, and leptomeninges. If cranial imaging is normal, lumbar puncture is certainly indicated in cases of thunderclap headache; subacute progressive headache; headache associated with fever, meningismus, confusion, or seizure; and high or low intracranial pressure. DIAGNOSIS: PRIMARY HEADACHE If worrisome or atypical features are not present and a secondary cause has been excluded, the IHS diagnostic criteria for migraine should be applied (Table 2). 8 When interpreting the IHS criteria, it is important to realize that there is no single criterion necessary nor sufficient for diagnosis and that any single criterion will be absent in up to 40% of patients. The IHS criteria do not require gastrointestinal symptoms for a migraine diagnosis, and Table 2. Diagnostic Criteria for Migraine Without Aura* A. At least 5 attacks fulfilling criteria B-D. Migraine days <15 days/month B. Migraine is defined as episodic attacks of headache lasting 4 to 72 hours C. With 2 of the following symptoms: Unilateral location Pulsating quality Aggravation by or causing avoidance from physical activity Moderate or severe pain intensity D. And 1 of the following symptoms: Nausea and/or vomiting Photophobia and phonophobia *Probable (migrainous) all but one of A-D. Data adapted with permission from Blackwell Publishing. 8 Table 3. Diagnostic Criteria for Migraine Aura (Typical, Hemiplegic, Basilar) A. At least 2 attacks fulfilling B-E B. Fully reversible visual and/or sensory and/or speech symptoms but no motor weakness C. At least 2 of the following: Unilateral symptoms including positive and/or negative features At least 1 symptom develops gradually over a period >5 minutes and/or different symptoms occur in succession Each symptom lasts >5 minutes and <60 minutes D. Headache meets criteria for migraine without aura and begins during the aura or follows aura within 60 minutes E. Not attributable to another disorder Data adapted with permission from Blackwell Publishing. 8 S552 Vol. 3 (6C) June 2003

vomiting occurs in less than one third of patients. While most migraine attacks are unilateral, 40% of patients report bilateral pain. Migraine is often described as nonpulsating, and only 15% of patients will have neurological aura associated with headache. Certain clinical features beyond the IHS criteria help to solidify a migraine diagnosis. For example, a temporal association with the menstrual cycle is frequent among migraine patients. Characteristic migraine triggers, including thirst or a food craving, may be present before the attack. Family history of migraine may be present, and a patient may have premonitory symptoms before an attack. A paradoxical relationship with sleep is frequent with migraine occurring during sleep or upon awakening, but sleep may also abate an attack. 12 MIGRAINE AURA The IHS diagnostic criteria for migraine aura are shown in Table 3. 8 More than one aura symptom can occur in succession, so that a patient may have a visual aura followed sequentially by a sensory symptom, such as paresthesia or speech difficulty. Certain conditions can produce symptoms that mimic migraine aura. These include stroke and transient ischemic attack (TIA), seizure disorders, tumors, venous thrombosis, arteriovenous malformation, and carotid artery dissection. Particularly common may be the need to differentiate migraine aura from TIA, as shown in Table 4. 13 The symptoms of TIA and other migraine aura mimics will usually violate several of the clinical rules for migraine diagnosis: they are irreversible; onset is abrupt, with lack of evolution; aura symptoms last for more than 60 minutes; a delay of more than 60 minutes occurs from the time aura begins to the time of headache onset. TENSION-TYPE HEADACHE Tension-type headache can be differentiated from migraine using IHS criteria. Tension-type headaches have a duration ranging from 30 minutes to 7 days and are not associated with nausea, photophobia, or phonophobia. In addition, at least 3 of the following 4 characteristics must be present for a tension-type headache diagnosis: pressing/tightening, nonpulsating quality; mild-to-moderate intensity that does not prohibit activity; bilateral location; not aggravated by routine physical activity. Table 4. Migraine Aura vs TIA Migraine vs TIA Positive visual symptoms Gradual onset/evolution Sequential progression Repetitive attacks of identical nature Flurry of attacks midlife Duration <60 minutes Headache follows ~50% TIA = transient ischemic attack. Adapted with permission from Fisher. 13 Table 5. Chronic Migraine Visual loss Abrupt Simultaneous occurrence Duration <15 minutes Headache uncommon accompaniment A. Average migraine frequency 15 days per month for 3 months fulfilling B-D B. Attacks fulfill criteria for migraine without aura C. No overuse of symptomatic drugs D. Not attributable to another disorder Data adapted with permission from Blackwell Publishing. 8 Figure 2. MRI Showing an Increased Diffusion- Weighted Signal in the Medial Left Occipital Cortex Consistent with Subacute Cerebral Infarction MRI = magnetic resonance image. Advanced Studies in Medicine S553

CHRONIC DAILY HEADACHE Any discussion of headache diagnosis and characterization must address chronic daily headache. While commonly used in clinical practice, chronic daily headache is not a diagnosis. Patients either have a primary chronic headache or a secondary chronic headache that may be posttraumatic, postinfectious, cervicogenic, or caused by vascular disorders or intracranial hypertension. 14 A similar approach using clinical clues can help to differentiate primary and secondary forms of chronic headache. It is estimated that between 4% and 5% of the US, European, and Asian populations have primary chronic daily headache defined as occurring on more than 15 days of each month, regardless of medication use. Primary chronic headaches cannot be related to another cause, such as structural or systemic disease. 15,16 A chronic daily headache of long duration (more than 4 hours) is most often primary headache and represents chronic migraine or tension-type headache. The IHS criteria for defining chronic migraine are shown in Table 5. 8 In clinical practice, approximately 78% of patients with chronic headache will have chronic migraine, and 15% will have chronic tension-type headache. Only 7% of such patients have chronic headache due to another cause. 14 Chronic daily headache of less than 4 hours duration is often secondary and may be due to paroxysmal hemicrania or hypnic headache. These patients typically present with an idiopathic stabbing headache. However, chronic daily headache of less than 4 hours can represent cluster headache. 14 The patient was postmenopausal and taking estrogen replacement therapy. Routine examination was normal, and CT revealed no brain abnormalities. She received an initial diagnosis of migraine with aura. However, upon a subsequent office visit, review of the clinical clues associated with worrisome features shown in Table 2 raised suspicion that there was a secondary etiology. The patient had neurological symptoms manifesting as aura and, although previous episodes of aura had lasted less than 20 minutes, with this episode, aura was persistent, representing a pattern change. In addition, the characteristics of this patient s current headache violated several of the clinical rules for migraine aura shown in Table 3. The neurological symptoms were not reversible, onset was abrupt rather than gradual, aura symptoms persisted for longer than 60 minutes, and there was a delay of more than 60 minutes from the time aura began to the time of the onset of headache pain. Investigations were conducted to rule out conditions that may mimic migraine aura. Electrocardiogram, coagulation studies, cerebral spinal fluid, and transesophageal echocardiogram were normal. Normal or negative values were found for erythrocyte sedimentation rate, antinuclear antibody, antineutrophil cytoplasmic antibodies, anti-doublestranded-dna antibodies, and anticardiolipin antibodies. However, a 4-vessel angiography revealed an irregularity in the left posterior cerebral artery. MRI also revealed an increased diffusion-weighted signal in the medial left occipital cortex that was consistent with a subacute cerebral infarction (Figure 2). Thus, a secondary cause of this particular headache was confirmed. CASE STUDY This case illustrates the accurate characterization of a particular headache using diagnostic criteria and clinical clues. A 46-year-old woman with a history of migraine aura without headache pain reported 3 such episodes during the past 6 years, each lasting 20 minutes in duration. She presented to the emergency department with an abrupt aura consisting of a right, homonomous scintillating scotoma followed by leftsided headache with nausea, and photophobia that had lasted 2 days. CONCLUSION Most headache cases seen in primary care will be due to a primary headache disorder, such as migraine or tension-type headache. Primary headache syndromes are diagnosed by defining the clinical features of an individual s attacks and applying them to the established definitions, or clinical rules for diagnosis, established by the IHS. If care is taken to identify any worrisome features present during a particular headache attack, the chances of missing the diagnosis of a secondary headache caused by a serious disorder can be greatly diminished. S554 Vol. 3 (6C) June 2003

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