Final answer:
The symptoms described are consistent with transverse myelitis, an inflammatory condition affecting the spinal cord. The presence of mononuclear cells and increased protein level in the cerebrospinal fluid supports the diagnosis. The combination of a preceding flu-like illness and the CSF findings suggest an acute infective cause.
Step-by-step explanation:
The symptoms described in the question, including progressive weakness and numbness of the legs and feet, increased lower extremity deep tendon reflexes, and urinary incontinence, are indicative of a neurological condition called transverse myelitis. Transverse myelitis is characterized by inflammation of the spinal cord that can result in weakness, sensory disturbances, and loss of bladder and bowel control.
The findings of increased deep tendon reflexes and extensor plantar reflexes suggest an upper motor neuron (UMN) lesion. The presence of mononuclear cells and increased protein level in the cerebrospinal fluid (CSF) obtained from a lumbar puncture (LP) are consistent with inflammatory changes in the central nervous system (CNS).
The combination of flu-like illness preceding the neurological symptoms and the CSF findings support an acute infective cause, such as a viral infection, as the underlying trigger for the transverse myelitis.