Stedman's Spellchecker Plus ($100) is a good product for health care professionals using NaturallySpeaking with either Word or WordPerfect. See http://www.stedmans.com for details and to purchase. It is a spellchecker -- nothing else. It can help you avoid mistakes in your documentation.
Without this spellchecker, many medical terms will show up as typos within Word or WordPerfect, making proofing of your work more difficult. With it, the words identified as typos will typically be odd names or typos.