cause unknown CO2 narcosis

The patient is a 92 years old female suffering from cause unknown CO2 narcosis. She came to this hospital for rehabilitation after a lumbar compression fracture.

3 days after she came to this hospital, she caused CO2 narcosis. According to the letter of reference, she was diagnosed as COPD(chronic obstructive pulmonary disease) although she never smokes. Her respiratory assistant muscle is not developed. We could hear coarse crackles in her lungs though we don’t know why. There is no sign of pulmonary enphysema in CT scan.  From these observations above, we concluded CO2 narcosis is not caused by COPD.

We suspected she has some sort of neuromuscular disease. We checked respiratory function test. That test says she has restrictive lung disease. She doesn’t have honey cone lung in CT scan. Fine crackles are not heard. As you can see, structural disorder is seemed to be negative. For these reasons above, we decided to consult Neurologist.

I observed his neurological examination. His knowledge is so sophisticated that I admired so much. I learn some new technique of neurological examination. He realized her muscle weakness of proximal muscle, so he doubted that she has myopathy, but her CK level is normal not high. There are no neurological signs which indicate ALS or MG.  In the end, it is difficult to diagnose what happened to her body.

Tell me if you have any other differential diagnosis.