Cranial nerve palsy and lower limb weakness – An unusual presentation of occult testicular lymphoma.

Clinical History

A 48-year-old man presenting with progressive lower limb weakness and multiple cranial nerve palsies was referred for neuroimaging by the Neurology department. He was otherwise well with no other clinical abnormality and no relevant past medical history. He had no scrotal symptoms.

Imaging Findings

MRI head and spine including gadolinium imaging showed pathological enhancement of cranial nerves (III, V and VIII), leptomeningeal surface of the cervical spine and the cauda equine [figures 1-5]. The differential diagnosis including inflammatory and neoplastic processes was considered but after correlation with lumbar puncture findings, malignancy was placed higher in the differential.

Whole body computed tomography (CT) was unremarkable. A positron emission tomography (PET-CT) scan was preformed. This demonstrated high tracer uptake from spinal nerves, cord surface, cauda equina, left testis and adrenals glands, due to disseminated disease [figures 6 A-C, 7]. The highest uptake was noted to be within the left testicle [figure 7].

Ultrasound of the testes identified an ill-defined low echo poor focus in the left testis, corresponding to the PET findings [figure 8]. Core biopsy of the left testis allowed histologically proven non-Hodgkin’s lymphoma (NHL). A presumptive diagnosis of primary testicular NHL with leptomeningeal dissemination was made.

Discussion

Neurolymphomatosis (NL) is the term applied to infiltration of the nervous system by lymphoma and non-tumour lymphocytes cells. [1] 90% of the cases of NL have been related to Non-Hodgkin’s Lymphoma (NHL). [2] Approximately 50% of the patients with central nervous system (CNS) metastases from NHL have progressive systemic lymphoma at the time of diagnosis of their CNS manifestation. The remaining 50% develop systemic disease within months. [3]

Primary testicular lymphoma is a rare but highly aggressive disease, representing 5-9% of all testicular tumours, with a 5-year survival rate ranging from 16-50%. [4, 5] Approximately two-thirds of the patients present with leptomeningeal spread and as shown in this case, leptomeningeal spread can often involve the cranial nerves, spinal cord surface, or spinal nerve roots and may present with cranial or spinal neuropathy.

Central nervous system lymphoma can be diagnosed with gadolinium-enhanced MRI with leptomeninges, ependyma, dura, or cranial nerves being the typical finding. There may be intrinsic superficial cerebral lesions and communicating hydrocephalus. It is recommended that any pre-emptive lumbar puncture is performed after MRI imaging of the CNS, to avoid false positive cranial or dural enhancement due to the lumbar puncture. [4]

MRI typically shows enhancement of affected nerves, and occasionally enlargement, as shown in this case, with the third nerve [figures 1] (arrow). MRI does not always provide ideal visualisation of lymphomatous involvement of peripheral nerves and therefore 18F-FDG PET/CT should be performed to complete the radiological staging. [6] Sensitivity and specificity of 18F-FDG PET/CT for the initial staging of NHL is reported to be 97 and 100%, respectively and is increasingly becoming a key part of the investigation of NHL. [3, 7]

As highlighted in this case, the presentation of neurolymphomatosis and staging of NHL, requires integrating information gained from MRI, 18F-FDG PET/CT, CSF cytology examination, but most importantly a high index of suspicion by the clinician and radiologist.

Differential Diagnosis List

Final Diagnosis

Non-Hodgkin’s Lymphoma

URL:	https://www.eurorad.org/case/11736
DOI:	10.1594/EURORAD/CASE.11736
ISSN:	1563-4086