The most common direct CNS involvement of ALL is leptomeningeal metastasis. Leukemic meningitis can affect the cerebral hemispheres, the cranial nerves or the spinal cord, and roots. Nerve root involvement can cause acute onset weakness and can be mistaken for  acute motor neuropathies such as GBS.

A 29 year old right handed male presented to the emergency department (ED) with one week history of bilateral lower extremity weakness right worse than left and numbness. The patient reported that he had been seen in the ED approximately one week earlier with upper respiratory symptoms and vomiting.  

Examination revealed normal strength in the arms.  In the legs, hip flexors, knee flexors and  extensors were grade 4 bilaterally. Dorsiflexion was grade 3 on the right and 4 on the left.  DTRs were 2+in the arms and absent in the legs. Sensation was diminished in a stocking distribution bilaterally.

MRI lumbar spine with contrast revealed diffuse nerve root prominence with  enhancement. Lumbar puncture revealed protein 134 mg %, glucose <10 mg %, nucleated cells 2145, numerous atypical lymphoid cells with an abnormal B-cell lymphoid population with dim CD45 staining expressing CD19, CD20, CD10 and cytoplasmic lambda light chain. CT neck, chest, abdomen, and pelvis with contrast were unrevealing.  

Based on the clinical presentation GBS was suspected and patient was started on IVIg infusion . However, subsequent oncological investigation confirmed the diagnosis of ALL and treatment was started.