Paraneoplastic neurological syndromes associated with Hodgkin (HL) and non-Hodgkin lymphomas (NHL) are uncommon and have been mainly reported as case reports. Paraneoplastic motor neuronopathies were first reported in 1963, with a disease course independent of the underlying malignancy. Patients with this syndrome typically develop leg greater than arm proximal motor weakness, with a diagnosis of lymphoma usually following the neurological presentation.

We describe a patient case of a non-Hodgkin B-cell lymphoma-related paraneoplastic severe motor neuronopathy.

A 70-year-old man developed progressive diffuse atrophy and weakness several months after the diagnosis of NHL. On initial neurologic examination in our clinic, he had severe diffuse symmetric limb weakness and atrophy with general hypotonicity. No fasciculations were observed in cranial or other muscles. Deep tendon reflexes were absent, except for reduced biceps responses. Sensation to large and small fiber modalities was intact except for slight reduction in timed vibration distally.  Nerve conduction studies (NCS) demonstrated a primary axonal disorder with motor far exceeding sensory involvement. Needle electromyography (EMG) demonstrated evidence of diffuse severe ongoing denervation and mild reinnervation. Symmetric enhancement of cervical spinal nerve roots was notable on magnetic resonance imaging (MRI). A final diagnosis of paraneoplastic motor neuronopathy was made after investigations for alternative causes of motor neuropathy and neuronopathy returned unrevealing. After a brief initial improvement, the patient ultimately failed to demonstrate a sustainable response to immunotherapy which included attempts to treat his underlying B-cell lymphoma. 

Paraneoplastic motor neuronopathy, although rare, should be considered in the differential diagnosis of patients with NHL presenting with a motor-predominant peripheral nerve disorder. Although severe and diffuse weakness usually precedes the diagnosis of malignancy, this case provides an example of motor neuronopathy following the diagnosis of NHL. Early identification of paraneoplastic neuronopathy is important as it may prevent unnecessary interventions and may guide therapeutic strategies.