Amnesia, fugue, and multiple personality disorders share this characteristic.

Physical Findings & Clinical Presentation

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Dissociative amnesia (DA): Loss of autobiographic memory for previous experiences or before a certain point in time. Types of DA include:

Localized amnesia: Inability to recall a specific (traumatic) period of time.

Selective amnesia: Inability to recall parts, but not all, of a specific period of time.

Systematized amnesia: Inability to recall categorical autobiographical memories, but not memory loss in chronologic order such as with localized amnesia.

Continuous amnesia: Anterograde loss of memory, or inability to remember successive events as they occurred.

Generalized (global) amnesia: Inability to recall one’s whole life, including personal details.

Thematic amnesia (as seen in DID and dissociative disorders not otherwise specified [DDNOS]): As identity states change, ability to recall specific periods of time is altered.

Dissociative fugue (DF): DF carries the same characteristics as DA, with the distinguishing feature of sudden and unplanned purposeful travel away from one’s home.

Dissociative identity disorder (DID): Formerly referred to asmultiple personality disorder (MPD), patients appear to possess two (or more) distinct identities or personality states, associated with the patient’s consciousness, perception, thoughts, and actions.

Depersonalization disorder (DPD): Also known asderealization disorder, DPD is a state in which patients believe that they have been altered in some way or that they are no longer real. Features include persistent and recurring experiences of feeling detached from one’s own body and mental processes (i.e., one observing oneself as an outsider). Reality testing remains intact.

Dissociative disorders not otherwise specified (DDNOS): Some dissociative symptoms of varying degrees but not meeting criteria for a distinct diagnosis.

Dissociative Fugue (Psychogenic Fugue)

Dissociative fugue is characterized by the sudden, unexpected travel away from home or one's customary place of daily activities, with inability to recall some or all of one's past. As in the previous disorder, amnesia is present, causing a sense of confusion about personal identity. On occasion, patients assume a new identity.

In contrast to dissociative amnesia cases, patients suffering from fugue states appear normal to the lay observer. Patients usually exhibit no signs of psychopathology or cognitive deficit. Fugue patients differ from those with dissociative amnesia in that the former are usually unaware of their amnesia. Only upon resumption of their former identities do they recall past memories, at which time they usually become amnestic for experiences during the fugue episode. Often, patients suffering from fugue states take on an entirely new (and often unrelated) identity and occupation. In contrast to patients suffering from DID, in fugue states the old and new identities do not alternate.

Not much is known regarding the etiology of this disorder. Nevertheless, the underlying motivating factor appears to be a desire to withdraw from emotionally painful experiences. Clinical data suggest that predisposing factors include extreme psychosocial stress such as war or natural and man-made disasters, personal and/or financial pressures or losses, heavy alcohol use, and intense and overwhelming stress such as assault or rape. The onset of some fugue episodes may occur during sleep or be associated with sleep deprivation.

As in cases of acute dissociative amnesia, the onset of the disorder is usually associated with a traumatic or overwhelming event accompanied by strong emotions such as depression, grief, suicidal or aggressive impulses, or shame. Dissociative fugue is the least understood dissociative disorder. This may be due to the fact that most of these patients do not present for treatment. Usually they do not come to the attention of medical personnel until they have recovered their identity and memory and return home. Typically, patients seek psychiatric attention once the fugue is over and they are seeking to recover their original identity or retrieve their memory for events that occurred during the fugue.

Dissociative Disorder Not Otherwise Specified

This category is reserved for presentations in which the predominant feature is dissociation without meeting criteria for any specific dissociative disorder. (Box 35-8 lists the DSM-IV4 criteria of this condition and exclusions to it.Box 35-9 lists the DSM-5 update for this disorder Other Specified/Unspecified Dissociative Disorders.) Examples of dissociative disorder NOS vary widely. Additionally, symptoms that result from torture or brainwashing may be classified in this category. Ganser's syndrome (sometimes called “prison psychosis”) is classified as a dissociative disorder NOS. It is characterized by the provision of approximate answers: that is, offering half-correct answers to simple inquiries, such as answering “Five” to the question, “What is two plus two?” The correct set of the response is given, but the answer is inaccurate. Ganser's syndrome is often reported in incarcerated populations.31–33

Finally, certain culture-bound syndromes (such asamok in Indonesia orlatah in Malaysia) are often characterized by dissociation and sometimes by violence. These syndromes have often been characterized as dissociative disorder NOS.

Hypnosis

This modality is especially useful in the reenactment of stressful or traumatic situations causing dissociative amnesia and dissociative fugue with memory loss. Hypnosis is best utilized to explore the events that precipitated the fugue or amnesia. When employing this technique, clinicians should suggest to the hypnotized patients that they may choose to forget some or even all of what was remembered or reenacted in the trance state to prevent them from being overwhelmed by the emergence of unconscious material that the patients are not yet ready to handle. The recaptured or selectively shared data from patients are then dealt with in the fully conscious state to help them cope with the underlying conflicts. It is generally advisable to employ other conscious methods before resorting to the use of hypnosis or chemical means to bring about a reenactment of a traumatic situation. While hypnosis is usually safe to use with most healthy individuals, the therapist or treater should exercise the same degree of caution in probing unconscious material in psychotherapy.

Examination of Attention and Orientation

Testing of orientation to time is more sensitive to cerebral dysfunction than testing of orientation to place, and impaired orientation to person should raise the possibility of a psychogenic fugue state. Successful completion of tests of orientation requires intact memory and expressive language; that is, these are not “pure” tests of attention. When time orientation is tested, orientation to the approximate time of day (within 1 hour), should be assessed as well as that to the day of the week, month, and year, and is perhaps the most reliable and sensitive. Disorientation as to the exact date has a very high base rate in the normal population and is rarely clinically useful. Marked disorientation to time is most common in patients with delirium or Korsakoff's amnesia. Orientation is often preserved in early dementia.

Attention has traditionally been tested by serial subtraction tasks and reverse spelling of words, such the serial sevens and “WORLD” backwards tasks in the MMSE. Such tasks are dependent on working memory, as well as on calculation and spelling, respectively, both of which are strongly related to educational background and both of which may be disrupted by focal lesions that do not otherwise impair attention.123 Reciting an overlearned sequence such as days of the week or months of the year in reverse order requires sustained attention and intact working memory; this test is very sensitive to disturbance of attentional processes and is generally understood across cultures and languages. Repeating a spoken sequence of digits, starting with two digits and increasing the length of the sequence with each correct attempt, is also a sensitive marker of attention, particularly when the patient needs to repeat the sequence in reverse, which is more difficult and places a greater load on working memory. Most subjects correctly complete 7 ± 2 digits forward and 5 ± 1 in reverse. Digit span testing depends on intact working memory, the frontal lobe–mediated brief store of visual or auditory information in current consciousness (e.g., remembering a telephone number before writing it down). Continuous performance tasks, which require the patient to respond when a particular stimulus is presented (e.g., the letter “A” in a list of random letters read by the examiner9) are minimally dependent on working memory but are good measures of sustained, directed attention. Finally, it is important for the clinician to be aware that attentional impairment may impair performance in other parts of the cognitive examination. If attention is markedly impaired, poor results on testing in other domains may not necessarily indicate that function in those domains is also impaired (Table 1-3).

Types of Dissociative Disorders Associated with Sleep

There are five diagnostic categories of DDs in DSM-IV47 including (1) dissociative identity disorder (formerly multiple personality disorder), (2) dissociative fugue, (3) dissociative amnesia, (4) depersonalization disorder, and (5) dissociative disorder not otherwise specified (DD NOS). Of these, three are considered SRDD: dissociative identity disorder, dissociative fugue, and DD NOS. Most but not all patients with SRDD have both daytime DD episodes as well as previous episodes of SRDD.1,48