Post-dural puncture headache with nerve root irritation or arachnoiditis: Given the patient's recent history of epidural placement for labor, followed by a CSF leak treated with a blood patch, it is plausible that she is experiencing complications related to the procedure. The symptoms of lower extremity weakness, especially after a CSF leak and its treatment, could be indicative of nerve root irritation or arachnoiditis, which is an inflammation of the arachnoid membrane that surrounds the spinal cord.

Infection (meningitis or epidural abscess): The patient's symptoms of chills and lower extremity weakness, combined with a recent invasive spinal procedure, raise the concern for an infectious process such as meningitis or an epidural abscess. The history of a CSF leak and subsequent blood patch increases the risk of introducing bacteria into the spinal canal.
Spinal epidural hematoma: Although less common, a spinal epidural hematoma could occur, especially in the context of recent spinal procedures. This condition would require urgent intervention to prevent permanent neurological damage.
Lumbosacral radiculopathy: Direct irritation or compression of the nerve roots in the lumbosacral spine could result in lower extremity weakness. This could be related to the patient's recent medical history or an independent condition.

Spinal cord infarction: This is a rare but potentially devastating condition that could present with acute lower extremity weakness. It is crucial to consider this diagnosis, especially given the patient's recent history of spinal procedures, which might increase the risk of vascular complications.
Cauda equina syndrome: Although the patient denies urinary or bladder incontinence, cauda equina syndrome is a condition that requires prompt recognition and treatment to prevent permanent neurological damage. It involves compression or damage to the nerves in the cauda equina, which could result from a variety of causes including infection, hematoma, or direct trauma.
Multiple sclerosis: An initial presentation of multiple sclerosis could involve neurological deficits such as lower extremity weakness. Given the patient's age and the nature of her symptoms, this diagnosis should be considered, especially if other causes are ruled out.

Neurosarcoidosis: This condition involves inflammation of the nervous system due to sarcoidosis and could present with a wide range of neurological symptoms, including lower extremity weakness.
** Guillain-Barré Syndrome**: An autoimmune disorder that could follow a recent infection, leading to ascending paralysis. The patient's symptoms of lower extremity weakness and recent history of a medical procedure might raise this consideration, although it is less directly related to her recent spinal procedures.

Complete Blood Count (CBC): To evaluate for signs of infection or inflammation.
Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP): To assess for inflammatory processes.
Blood cultures: If there is a suspicion of infection.
Lumbar puncture (LP): If not contraindicated, to evaluate for infection, inflammation, or other abnormalities in the cerebrospinal fluid.
Magnetic Resonance Imaging (MRI) of the spine: To evaluate for structural abnormalities, infection, or inflammation affecting the spinal cord or nerve roots.
Urgent neurology consultation: Given the potential for serious neurological conditions, early consultation with a neurologist is advisable.
Monitor neurological status closely: Regular assessment of the patient's neurological function, including strength, sensation, and bladder/bowel function, is crucial for early detection of any deterioration.