Here are bits and pieces of an article about Dissociative Amnesia from the blog: TraumaDissociation.com.
Dissociative Amnesia Dissociative amnesia is the most common Dissociative Disorder. There are several different types of amnesia, and many different causes. Dissociative Amnesia is not caused by head injuries or physical damage to the brain, it is amnesia which has a psychological cause. It can occur as part of a number of other mental health conditions, including posttraumatic stress disorder and acute stress disorder, dissociative identity disorder, somatoform disorder, and anxiety disorders, :298,  in any of those cases it would not be classed as a separate disorder. Dissociation Amnesia can last for between a few days to a few years, but is typically less than a week. The period of time which cannot be remembered can range from minutes to decades. Read more: http://traumadissociation.com/dissociativeamnesia
Because there is no neurobiological damage or toxicity, and the difficulties are in retrieving a memory which was successfully stored, the amnesia is always “potentially reversible”. :298-299,  Neurocognitive disorders involving memory loss usually include cognitive (thinking) and intellectual impairments in memory, these are not present in people Dissociative Amnesia. :300-301 Dissociative amnesia is more likely in people with a history of multiple adverse childhood experiences (especially if they include physical or sexual abuse), people who have experienced interpersonal violence (for example, domestic violence or physical assaults), and the risk increases with the “severity, frequency, and violence of the trauma”. :298-299 Clinical interviews to diagnose Dissociative Amnesia include the SCID-D (revised) by Dr Marlene Steinberg, and the Dissociative Disorders Interview Schedule (DDIS). Both of these are capable of diagnosing any dissociative disorder and a number of other disorders as well. :124 Read more: http://traumadissociation.com/dissociativeamnesia
The three common types of dissociative amnesia are localized amnesia, selective amnesia (which may occur along with localized amnesia), and generalized amnesia. Generalized amnesia may involve the complete loss of a person’s identity, in addition to all memories of their past. Other forms of dissociative amnesia can also occur; people with generalized amnesia (the most severe type) may also lose semantic knowledge (previous knowledge about the world) and procedural knowledge (forgetting well-learned skills). :298-299 Systematized amnesia is amnesia for a category of information (e.g., no memory of family, no memory of a specific person, or childhood sexual abuse). Continuous amnesia is unable to form new memories. :298-299 Micro-amnesias are also typical in dissociative disorders, the amnesia is for very, very brief periods of time. The International Society for the Study of Trauma and Dissociation gives the example of forgetting the contents of a conversation from one moment to the next. The person may struggle to work out what was discussed while trying to avoid the other person realizing this.  Dissociative Amnesia has been previously known as Psychogenic Amnesia, and Hysterical Amnesia. Read more: http://traumadissociation.com/dissociativeamnesia
Dissociative amnesia occurring with fugue should be treated as soon as possible; psychotherapy is the recommended treatment. This should involve a safe environment for therapy and a strong therapeutic alliance. Treatment goals include the recovery of the person’s identity, identifying the triggers linked to the start of the fugue, and working through the traumatic material. Medication given during interviews, and hypnosis may be also help. Recovery is often rapid.  When memories begin to return a person often experiences emotions such as grief, rage, shame, guilt, depression and inner turmoil. Many people with Dissociative Amnesia develop Posttraumatic Stress Disorder at some point in their lives. :302 Read more: http://traumadissociation.com/dissociativeamnesia