Paraneoplastic sensorimotor neuropathy and ventral cauda equina nerve root enhancement as initial presentation of small cell lung carcinoma: a case study

BACKGROUND

Paraneoplastic neurologic syndromes (PNS) are rare, however, are important to recognize as oftentimes they precede the detection of an occult malignancy. Our case highlights a rare circumstance of paraneoplastic radiculoneuropathy and the importance of recognizing PNS in antibody negative disease, as is the case in up to 16% of sensory neuronopathies, and the process of excluding other etiologies.

CASE PRESENTATION

We discuss a 51-year-old man who presented with asymmetric subacute sensorimotor deficits in the lower limbs. Initial clinical examination showed weakness throughout the right lower limb and normal strength on the left with objective numbness in a mixed dermatomal and stocking-glove distribution. Electrophysiology was consistent with axonal sensorimotor neuropathy. Cerebrospinal fluid showed pleocytosis and elevated protein. Intravenous immunoglobulin treatment was given with some improvement in pain symptoms but no measurable motor improvement. Following clinical and electrophysiologic deterioration the patient was transferred to a tertiary centre. Magnetic resonance imaging of the spine showed smooth enhancement of the ventral caudal nerve roots. Chest computed tomography revealed left lower vascular scarring. Further positron emission tomography scan imaging identified fluorodeoxyglucose avid right lung lymphadenopathy. Bronchoscopy-guided biopsy revealed small cell lung carcinoma. Onconeural and antiganglioside antibodies were negative. The patient was then transferred to a medical oncology ward where he underwent chemoradiotherapy and subsequently experienced improvement in his motor function, supporting that his neurological condition was indeed secondary to a paraneoplastic process.

CONCLUSIONS

Onconeural negative paraneoplastic radiculoneuropathy can precede diagnosis of small cell lung carcinoma. If considered early and adequately investigated, it can allow earlier diagnosis and treatment of underlying malignancy, improving overall and neurological prognosis.

Paraneoplastic mononeuritis multiplex in non-small-cell lung carcinoma

A 60-year-old man developed two selective peripheral mononeuropathies of the peroneal and later the radial nerve, shortly after a diagnosis of large-cell lung carcinoma. Nerve conduction studies and electromyography confirmed isolated lesions in both nerves, and in the case of the peroneal nerve lesion, focal conduction block was localised to the level of the fibula neck. Subsequent magnetic resonance imaging of the lower limb excluded focal compression or malignant infiltration along the course of the peroneal nerve, and there was no signal change within the nerve, prompting a diagnosis of paraneoplastic mononeuritis multiplex. Anti-neuronal antibodies and serological markers of systemic vasculitis were negative. Neither the patient's large-cell lung carcinoma nor mononeuritis multiplex responded to chemotherapy, and he died within 6 months of the initial diagnosis.

Antibody-positive paraneoplastic neurologic syndromes: value of CT and PET for tumor diagnosis

OBJECTIVE

To assess use of whole-body 18F fluoro-2-deoxy-glucose (FDG)-PET and CT for diagnosing tumor in patients with antibody-positive paraneoplastic neurologic syndromes (PNS).

METHODS

In order to directly compare CT and FDG-PET imaging in patients with various antineuronal antibodies, the authors performed in parallel CT scanning and FDG-PET in a series of 13 consecutive patients (9 women, 4 men, aged 59 +/- 14 years) with positive antineuronal antibodies (anti-Hu: 8, anti-Yo: 4, anti-Tr: 1) in whom the authors were searching for a tumor or tumor recurrence.

RESULTS

A new tumor or tumor recurrence was found in 10/13 patients (5 small cell lung cancer, 2 ovarian cancer, and 1 each neuroblastoma, Hodgkin's lymphoma, and lymph node metastasis of adenocarcinoma). All tumors except one with good clinical evidence for small cell lung cancer were confirmed histologically. For detection of tumor or tumor recurrence, CT was positive in 3/10 patients (sensitivity of 30%), and FDG-PET in 9/10 (sensitivity of 90%, difference between methods p < 0.01), but the combination of both methods showed a sensitivity of 100%.

CONCLUSIONS

FDG-PET imaging is useful in tumor screening of patients with antineuronal antibodies, but should be complemented by CT scanning to increase sensitivity and accuracy of tumor diagnosis.