ASSESSMENT AND MANAGEMENT PRINCIPLES

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CHAPTER 52 ASSESSMENT AND MANAGEMENT PRINCIPLES

By virtue of their capacity to divert the functionality of neural networks into clinically overt discharges, epileptic seizures represent a fascinating window onto brain functions and also the source of a virtually infinite variety of ictal manifestations. The epilepsies encompass a large variety of syndromes reflecting a multitude of brain lesions as well as gene and protein dysfunction that results in neuronal hyperexcitability. An ever-increasing understanding, described in an exponentially growing number of dedicated textbooks, translates into a capacity for more precise diagnosis and optimization of syndrome-dependent management, compounded by the flurry of antiepileptic drugs made available for seizure treatment in the last two decades.

However, the unique complexity of this common neurological disorder has created a major gap in knowledge between the few specialists who manage to keep comprehensively abreast of the multiple facets of seizures and epilepsies and most other physicians, including the majority of those primarily involved in the management of patients with newly diagnosed seizures. It is not possible to familiarize general practitioners, pediatricians, general physicians, or even general neurologists with the entire spectrum of epileptic disorders. On the other hand, it is dangerous to oversimplify the problem of seizures by ignoring major challenges that result from the diversity of epileptic disorders.

Facing this dilemma, our aim is to provide a practical and effective guide to the diagnosis and management of the epilepsies for physicians who do not intend to become specialists in the field but are required to offer the best possible care to their patients with epilepsy. This chapter therefore. concentrates on general issues, rules, and procedures that help prevent misdiagnosis or inappropriate management rather than listing all seizure types and epilepsy syndromes, illustrating points with typical examples. More detailed information regarding specific types of epilepsy syndromes and their etiologies is provided in other chapters in this section. This chapter also concentrates on the diagnosis and management of newly affected patients.

The diagnosis of epileptic seizures and epilepsy often proves difficult, reflected by an average delay of several years between the first seizure and accurate diagnosis. In juvenile myoclonic epilepsy, where subtle myoclonic jerks often precede the occurrence of a first generalized tonic-clonic seizure (GTCS) by many years, this average delay lies between 6 and 15 years. Similarly, epilepsy is unlikely to be diagnosed in patients with simple partial seizures solely characterized by experiential auras or by distressing rising epigastric sensations, with the latter often wrongly considered manifestations of an anxiety disorder. Overall, it is believed that up to 20% of patients with epilepsy remain undiagnosed. Conversely, many patients with nonepileptic seizures are falsely considered to have epilepsy. Approximately 20% of patients seen at epilepsy referral centers for drug-resistant attacks eventually prove to have psychogenic nonepileptic seizures. The mean delay to diagnosis of this somatoform condition is around 7 years, implying that many patients with psychogenic nonepileptic seizures will inappropriately take antiepileptic medication, which by itself may result in serious adverse events. All of these pitfalls can be readily avoided with accurate observation and description of seizure semiology.

When the epileptic origin of seizures has been ascertained, another major diagnostic issue remains to be dealt with—identification of the epileptic syndrome. Identification is important so that the most appropriate treatment can be recommended and an accurate prognosis given. For example, idiopathic generalized epilepsy can be aggravated by the majority of antiepileptic drugs used for treating partial epilepsy and must therefore be distinguished from the latter. Another important example is the early identification of temporal lobe epilepsy with magnetic resonance imaging (MRI) signs of hippocampal sclerosis. This diagnosis predicts a high risk of developing refractoriness to antiepileptic drugs and suggests timely consideration of presurgical evaluation with a view to epilepsy surgery. Failure to do so will expose the patients to the danger of recurrent seizures and associated socioprofessional and familial stigmas for many years, if not decades. In the above two examples, the diagnosis of epileptic syndromes largely depends on the clinical description of seizures, the age at onset, and a detailed family and personal history. However, two other investigations greatly contribute to a correct diagnosis: electroencephalography which plays a major role in differentiating idiopathic generalized epilepsy from other forms of epilepsy, and more generally in defining epileptic syndromes, and MRI, which is the most sensitive way to detect an epileptogenic brain lesion.

DIAGNOSIS STEP 1: DEFINING THE SEIZURE TYPE(S)

The diagnosis of seizure type(s) relies mainly on a detailed chronological description of ictal signs and symptoms by the patient, relatives, and any other available witnesses. Other investigations are often unnecessary in arriving at an accurate diagnosis.

Investigating the Seizure Episode

One can compare the process of gathering all potentially relevant information about a seizure episode with a detective investigation. Indeed, it is of primary importance to get a vivid, movie-like, corroborated description of the “seizure scene,” as if one had actually been there, to avoid neglecting potentially informative details. This approach is limited in specific situations such as unwitnessed nocturnal attacks that often leave patients amnesic of entire episodes, including the duration of any postictal confusion. But, in the majority of cases, patients can precisely describe their activity until seizure onset. It is useful to ascertain whether a patient was standing and for how long, whether engaged in conversation or in any other purposeful action, or whether an object was being held. Such contextual information provides a basis for interpretation of all subsequent changes in motor activity and behavior and might disclose a significant precipitating factor. The latter may operate on a time scale that varies from a few seconds in reflex seizures to about 20 minutes in the typical form of vasovagal syncope. Other seizure-favoring factors that operate on a larger time scale, such as sleep deprivation, alcohol withdrawal, or mood disorders, must also be sought, together with relevant past-history—they are discussed in the section on etiology.

Searching for Seizure-Precipitating Factors

Seizure-precipitating factors are not always reported by patients spontaneously and so must be specifically sought. In the most common type of photosensitive epilepsy, the identification of a triggering stimulus may be trivial in some situations, such as stroboscopic lightning at a dance party or a video game session, but can be harder to detect in the case of alternating sun exposure when driving along a line of trees or looking at an object characterized by a pattern of repetitive high-contrast figures. Similarly, in the much rarer primary reading epilepsy, an affected adolescent or young adult will not necessarily recognize the role played by reading aloud until several seizures occur under similar circumstances. Detailing patient activity prior to seizure onset offers the best opportunity for a physician to detect a seizure-triggering factor.

Apart from these examples, a variety of other sensory or cognitive stimuli may occasionally precipitate partial or generalized seizures. These include sudden unexpected noise responsible for startle-induced seizures, listening to specific pieces of music, playing chess, performing mental arithmetic, programming a particular gesture, and virtually any other mental process. One of our patients used to experience temporal lobe seizures when he heard or saw something related to the “past,” like an old song or a movie from the 1950s, regardless of their relation to his personal memories. Although patients may feel reluctant to consider or report such odd stimuli, physicians should equally be prepared for such oddities that primarily reflect the potential for any cortical neural network to generate seizures, including those involved in allocating times and dates to events in living experience.

One general rule applies to epilepsy—The more odd the experiential or behavioral phenomena, the more likely that they are of epileptic origin provided the presence of core features of an epileptic seizure are present (see later). Although counterintuitive, the “theatrical” semiology of psychogenic attacks usually proves less dramatic than that of partial seizures.

Validating the Core Features of Epileptic Seizures

Once the context of a seizure episode has been ascertained, and prior to its detailed description, one should confirm the presence of the core features that characterize almost all epileptic fits, such as an abrupt onset, a short duration of several seconds to a few minutes, and a stereotyped sequence of ictal signs and symptoms.

“Desperately Seeking” a Witness to the Seizure(s)

Witnessed accounts of seizures often provide essential information, complementary to that reported by patients. Even in simple partial seizures characterized by a rising epigastric sensation, witnesses can notice subtle oroalimentary automatisms (chewing or lip-smacking) of which patients are unaware. This example is particularly striking because the sole presence of oroalimentary automatisms allows a firm conclusion about the epileptic origin of a condition that might otherwise be considered an anxiety disorder, inasmuch as the scalp-electroencephalogram is usually normal in such types of limbic seizure.

Spontaneous narrative by nonmedical observers can be inadequate, so direct questioning is also needed. Efforts should always be made to directly question witnesses. A single telephone call can prove much more fruitful than costly medical examinations. The critical questions relate to the first detectable abnormal sign witnessed and whether there was any warning from the patient. Was there any detectable blush or pallor, change in respiration rate or facial expression, or head deviation? Were the eyes open with a fixed orientation or responsive to external stimulation (in favor of partial seizures), closed (in favor of nonepileptic seizures), or rolled upward (suggesting GTCS or syncope)? Were the arms still, or in a peculiar posture or gesture, or were they rhythmically moving? If a patient fell, was the fall abrupt or progressive, forward or backward, with legs bent or stretched, and was the fall followed by general hypotonia or hypertonia?

If “convulsions” are reported, their duration, type, and the amplitude of limb movements must be specified to distinguish GTCS from convulsive syncope and psychogenic attacks. In GTCS, clonic movements are characterized by tonic contractions of moderate amplitude that last approximately 30 seconds. In convulsive syncope, only one to five irregular clonic movements are observed during a few seconds. In psychogenic “convulsion-like” episodes, rhythmic limb movements typically resemble a large-amplitude tremor developing in the context of neutral or decreased muscular tone and often lasting several minutes.

If a seizure is primarily characterized by a lack of responsiveness, particular attention should be paid to the presence of automatisms, which, though often noticed, are infrequently reported spontaneously by witnesses. The diagnostic value of oroalimentary automatisms has been mentioned, the same is true for manual, pedal, and verbal automatisms, which all strongly suggest an epileptic origin for seizures. These automatic activities tend to imitate seemingly natural or purposeful gestures or speech, although they usually appear meaningless or inappropriate during a seizure. They must be distinguished from elementary motor activity leading to posture, change in muscle tone, clonic jerk, or a scream. In the 1989 classification of seizures and epilepsies, automatisms are specifically associated with complex partial seizures. In fact, as previously described, subtle automatisms may also occur during simple partial seizures and, at times, during absence seizures.

Classifying the Seizure Episode

Based on all the information gathered through investigation of a seizure episode, three clinical situations should be distinguished, providing a framework for the diagnostic process:

Seizures Associated With Complete Loss of Consciousness, a Fall, and Convulsive Features

This category includes “primary” GTCS, secondary generalized partial seizures, and the much less frequent generalized tonic, atonic, or clonic seizures. Distinction between primary and secondary generalized tonic-clonic seizures has important therapeutic consequences and can pose a difficult diagnostic problem. Differential diagnosis primarily includes syncope and psychogenic nonepileptic seizure.

“Primary” Generalized Tonic-Clonic Seizures

These typically start with a 10- to 20-second tonic phase characterized by a vocalization, intense tonic flexion, and then extension of all four limbs; the eyes roll upward, and apnea, which is responsible for subsequent cyanosis. The hypertonia intermittently resolves, giving rise to the clonic phase, which lasts approximately 30 seconds, and to the drooling of saliva. Clonic movements are characterized by tonic contractions of moderate amplitude and progressively decreasing frequency that finally cease. Patients remain hypotonic for several minutes; they may urinate and then resume loud labored breathing, reflecting the prior accumulation of bronchial and salivary secretions. Traces of tongue biting can then be observed. Their location on one or both sides of the tongue is highly suggestive of a GTCS, whereas biting the tip of the tongue can result from any traumatic fall. The long duration of postictal amnesia has been previously mentioned. Once patients recover, they may complain of diffuse muscle pain reflecting the intensity of tonic-clonic contractions, but the possibility of a seizure-induced shoulder dislocation should not be overlooked.

An important feature of primary GTCS is the lack of ictal signs or symptoms that suggest a partial onset. However, tonic head deviation may occur at the onset of primary GTCS, representing the only “focal” sign in this seizure type. In addition, patients with juvenile myoclonic epilepsy sometimes remember presenting bursts of increasingly intense generalized myoclonic jerks prior to the onset of GTCS. As detailed later, these myoclonic jerks represent another type of generalized seizure, with preserved consciousness, and should not be interpreted as an aura.

Differential Diagnoses

image Syncope can result from various pathophysiological mechanisms with a common endpoint being a decrease in cerebral perfusion responsible for acute cerebral and brainstem dysfunction. Vasovagal syncope is the most frequent and can be mistaken for GTCS. It typically occurs in adolescents and young adults following emotionally salient stimuli (pain, sight of blood during venous puncture, warm and enclosed atmosphere) or after standing motionless for prolonged periods (related to progressive venous blood sequestration in the lower limbs). Thus, vasovagal syncope usually occurs in the standing position and often aborts if a patient lies down in the early phase of an attack. More rarely, vasovagal syncope will occur in a seated patient at the end of a meal, triggered by digestion-induced splanchnic blood sequestration. Prodromes include vertigo, visual and auditory disturbances, nausea, sweating, and the feeling of an imminent fainting or death. Intense pallor and general hypotonia follow, resulting in a progressive nontraumatic fall and loss of consciousness, with eyes closed or rolled upward. At times, syncope might progress to brief axial hypertonia associated with a few irregular clonic limb movements (fewer than six), “convulsive syncope.” Urination and biting of the tip of the tongue can occur, but normal consciousness is restored much more rapidly than in GTCS. Thus, detailed analysis of all signs and symptoms usually results in a clear distinction of syncope from GTCS, even in the presence of clonic movements, urination, and tongue biting. When necessary, a tilt test can be used to confirm the diagnosis of vasovagal syncope. Cardiogenic syncope represents a less frequent form of attack, observed in older patients with cardiovascular pathology but no other precipitating factors. It is characterized by a more abrupt loss of consciousness and fall.