My word, you certainly need to file for FMLA Leave. Please see the Legal Guide I published yesterday here on Avvo, which discusses your issue. Go to my profile, and look for the Legal Guides I published. Please look at the links I attached thereto as well. I think thereafter it would be a good idea to call our office, or that of a qualified Pennsylvania Employment Lawyer, without delay.
John is correct that it makes sense to request FMLA leave. Generally speaking, this is not required but it never hurts to be safe and make the request.
Since there is a nurse case manager, I assume that this claim has been accepeted by the PA WC insurance carrier. You should be receiving weekly indemnity (wage loss) benefits and having your medicals paid for your work related medical treatment.
At some point in time, there is going to be a request for you to return to work. If you don't return to work, your job could be filled by someone else and you could find your employment relationship ended. In the alternative, you are not able to return to work, your job is filled by someone else and your employment relationship is ended. This is where the FMLA request comes into play, to try to keep your job available to you when you are able to return to work.
Bottom line, it makes sense to sit down with an experienced WC attorney to review the facts of your claim with you and made sure that everything is in order. This should be your primary concern. After that, you can consider secondary issues like FMLA.
Remember that you employer and the nurse case manager are concerned about minimizing their risk as a result of your work injury. Taking advice from them is like talking to the fox that is guarding the hen house. Get your own advice from an attorney that you are comfortable with and best of luck to you!
In short, workers compensation laws do not protect your job in Pennsylvania, although it creates financial incentives that will cause your employer to offer you your job when yo recover the ability to perform it.
FMLA does provide formal job protection, for 12 months. You may want to "perfect" your request for leave by putting it in writing. If your employer does not act on your written request, you may not want to pursue the matter any further right away. If your employer responds, the 12 weeks of job protection runs concurrently with WC coverage. If they do not respond, you may be to "extend" the last date of job protection by waitning to see what happens. Timing of you pursuit of the FMLA benefits may be an important issue. You should discuss that with a lawyer familiar with both FMLA and WC laws if your employer fails to respond to your written request.