As you noted, the Health Insurance Portability or Accountability Act or HIPAA, which protects patient's medical records, sometimes also has the unintended effect of denying family members information they might
find useful in making decisions about their own medical care.
If your mother's Alzheimer's does not prevent her from understanding and signing legal documents, you might encourage her to sign a HIPAA release form. Many doctors, hospitals, and other healthcare providers have their own release forms that they will give patients to complete to authorize disclosing all or some types of medical information. This site will also be offering a form you can complete and sign that complies with HIPAA's statutory requirements.
If, however, your mother's mental condition makes it impossible for her to knowingly consent to releasing this information, then you are pinned in a much tougher spot.
Your strongest option for help is the source you've probably tried unsuccessfully before: your mother's husband. Perhaps it's worth one more try at a heart to heart discussion in which you assure him that you are not attempting to get any decision-making power from him, but want to appeal to him as a concerned parent.
As a final resort, you might contact your mother's medical practitioners directly with your plea"”or get to them through the patient representative or ombudsman at the hospital or clinic with which they may be affiliated. While you may still not be able to get unfettered access to your mother's records this way, you may be able to get some medical advice and counsel about the likelihood of carrying or passing along particular conditions your mother may have.