Chapter 20: Dissociative Spells

Introduction

A large proportion of patients undergoing video-electroencephalography monitoring (VEM) do not have epileptiform electroencephalographic (EEG) changes during their spells, and approximately one third of patients admitted to tertiary care epilepsy monitoring units are ultimately deemed to have nonepileptic spells.^1,2 In a relatively small proportion of these patients, physiological causes for their events (e.g., cardiac arrhythmia and hypoglycemia) are found, and a majority of these patients are discharged with a definitive diagnosis of psychogenic nonepileptic seizures (PNES). Many other terms, as listed in Table 20-1, are used to describe the exact same phenomenon.³ The diversity of the terms used to describe this disorder makes it difficult to gain a comprehensive survey of the available literature. Additionally, there is considerable overlap of features present in PNES and those of other functional neurologic disorders, such as psychogenic movement disorder and psychogenic pain disorder. From the observation of this overlap, a spectrum of disorders is likely represented under the umbrella of conversion and somatization disorders.

What is unique to patients diagnosed with PNES compared with other functional neurologic disorders is that dissociative symptoms often predominate in the clinical presentation. This further complicates establishing the diagnosis because behaviors similar to dissociation occur in some complex partial seizures. Indeed, PNES that include other behaviors are more reliably distinguished from epileptic seizures (Table 20-2). Currently, PNES are described in the literature as a form of conversion disorder. This leads to the issue of whether patients with PNES manifested by dissociative symptoms should be diagnosed as having a conversion disorder or a dissociative disorder that has been misdiagnosed as epilepsy. That is, the patient who presents to a psychiatrist with dissociative symptoms diagnosed as dissociative disorder may be identical to the patient who presents to a neurologist and is diagnosed with epilepsy. However, in the patient presenting to a neurologist who is diagnosed with epilepsy, the diagnosis is later corrected to PNES. This begs the question: are some forms of PNES better classified as a dissociative condition rather than a conversion disorder?