Acute Disseminated Encephalomyelitis?

  In May 98, my 42-yr-old sister had a stroke (temporary paralysis of left side
  of face, inability to swallow, severe headache on left side, high blood
  pressure--motor skills were fine). In several MRIs, CTs, and spinal taps, no
  blood clots or aneurysms or indications of MS were found. The neurologist said
  that small white spots appeared on her spinal cord in the MRI in several
  places--i.e., where swallowing is controlled. About 3 days later her right arm
  started going numb and has since begun to translate touch and cold as pain. Her
  left eye still wanders. She has begun to have thinking/memory problems. She was
  recently diagnosed w/ central sleep apnea.
  Because she has had headaches and a fever every day since the first stroke, the
  dr. said she could have ADEM. I don't understand--doesn't "acute" mean that
  it was a one-time event? Why would her condition be worsening? Is it possible for
  her to still have a viral infection of some kind (which dozens of blood tests have
  failed to identify)that is making this "chronic" disseminated encephalomyelitis?
  If so, is there any way you know of to stop the demyelination if a virus can't be
  found and "cured" (though only the body can fight off a virus, right?)? Could she
  have ADEM even though she showed no sign of a viral infection before the stroke?
  If Devic's disease might be a possible cause, can you tell me more about it?
  Sorry for the long posting & the many questions--so many symptoms have developed
  since May, and without any idea of what is happening to her, I'm very worried
  things will keep getting worse. And thanks for whatever information you can give--Barbara

[CCF Neuro MD MJD]

This seems like a very complex situation especially for her doctors, so it's difficult to answer some of these things given the limitations of this venue, but I'll try to give you some information that may answer your questions.  It sounds like your sister has had an acute event with progression or a series of acute events in succession.  This could be from many causes - You mentioned "stroke" because the initial event was sudden onset, but certainly this is not a conventional stroke in the way we typically encounter them - they occur acutely, are maximal initially and then stays stable or improves.  But could your sister be experiencing a series of strokes affecting the deeper parts of her brain?  Why would this occur?  If your sister had a source of recurrent clot that travelled to her brain e.g. from her heart, this could cause multiple acute events that cause progressive worsening.  Other causes of multiple strokes would be Vascultits (inflamation (inflammation) of the blood vessels) - either from immunologic disease or infections.  Now remember, your doctors have more of a sense of her neurologic syndrome but if these multiple strokes are suspected , your sister should have a echocardiogram, blood cultures, spinal tap with culture, immunologic workup, and even an angiography to evaluate the blood vessels.
If your doctors feel from the radiographic and clinical impression this is demyelinating (lesions of the white matter), then ADEM is a possibility.  ADEM is not like multiple sclerosis - it is a monophasic and often significant problem - if the spine as well as the deep brain is involved, then demyelination certainly could be the underlying etiology.  Infection may be the initiator in ADEM, but basically a cascade of inflammation is triggered without clear evidence of infection.  Since the infection is not present at this point, ADEM does not respond to antibiotics. Rather, antiinflammatory agents such as Steroids are the treatment.  Note that some infections can affect the white matte and mimic ADEM so an evaluation with spinal tap with cultures needs to be done as well.
As for Devic's Disease, some people even question the identity of this diagnosis.  Wheter it is a separate entity for MS or not, it does not sound like your sister has either Multiple Sclerosis (though there is a rare version of "malignant" or rapidly progressive MS)or Devic's (Devic's would only involve the spine and optic nerves not the brain)
Although giving you a vague idea of the spectrum of diseases your sister might have, it does not clearly give you a sense of which of these are most likely.  Ask your sister's neurologist about these possibilities and what workup has been done to date.  I hope some of this has been of help.