Intracranial Leptomeningeal Carcinomatosis: A Diagnostic Study with 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography

18F-FDG Brain PET/CT Metabolic Imaging in Patients with Suspected Autoimmune Encephalitis (AE) in the Early Stage: Can the Procedure Play a Complementary Diagnostic Role?

Background/Objectives: Recent studies reported that 18F-Fluorodeoxyglucose (FDG) positron -emission tomography/computed tomography (PET/CT), even in comparison with other traditional methods, can play a role in diagnosing AE and supporting early treatment. In the present study, we further investigated whether 18F-FDG PET/CT may be a complementary diagnostic tool to conventional procedures in patients with acute symptoms of suspected AE in the early phase. Methods: Eleven consecutive patients with recent acute symptoms suggestive of AE were retrospectively enrolled and underwent brain PET/CT after receiving an intravenous injection of 3.7 MBq/kg of 18F-FDG. Results: PET/CT showed abnormal FDG uptake in 9/11 patients classified as AE, while it was negative in the remaining 2/11 cases with vascular lesions. Magnetic resonance imaging (MRI), conducted in only 10/11 cases-one patient was a pacemaker wearer-identified suspected AE areas in 3/10 cases, ischemic lesions in another 3/10, and nonspecific data in the remaining 4/10 cases. Cerebrospinal fluid (CSF) tests revealed autoantibody delayed occurrence only in three patients (anti-GAD65, anti-Ma2, and anti-LGI1). After first-line treatment, 3/9 patients showed clinical improvement. Another 3/9 patients experienced partial improvement but with recurrence and new AE brain areas identified by PET/CT, which also detected favorable responses to second-line treatment in 2/3 cases. The remaining 3/9 patients, who were not responsive to treatment, ultimately died. Conclusions: In this study, PET/CT was effective in early identification of AE and enabling rapid therapy, even with inconclusive MRI and persistently negative or delayed positive CSF tests. PET/CT may aid in evaluating treatment response and detecting relapse. Notably, a negative PET/CT was associated with AE absence.

Diagnostic challenges in neoplastic meningitis presenting as intracranial hypertension

A diagnosis of idiopathic intracranial hypertension should be considered only after careful exclusion of all possible aetiologies. We report a case of neoplastic meningitis presenting as intracranial hypertension with inconclusive repeated cerebrospinal fluid (CSF) cytology and MRI of brain, emphasising the importance of meticulous CSF analysis and role of early whole-body PET-CT scan for diagnosis of systemic malignancy.

Whole-body 18-F-FDG-PET in patients with leptomeningeal disease and correlation with MRI

OBJECTIVE

Studies evaluating leptomeningeal disease on whole-body 18F-FDG PET are lacking. The purpose was to evaluate PET imaging of leptomeningeal disease and investigate the incremental utility of newer PET reconstructions in leptomeningeal disease.

METHODS

PET imaging of 56 patients with leptomeningeal disease detected initially on MRI (n = 53) or cytopathology (n = 35) were retrospectively reviewed. Regular 3-dimensional iterative reconstruction (3D IR, n = 56) and advanced reconstruction (AdvRecon, n = 41) PET images were evaluated by readers blinded to clinical and MRI findings for uptake involving cauda equina, posterior fossa and spinal cord. Spinal cord uptake pattern was classified as normal (uptake < liver), uptake = liver, conus uptake > liver, conus and cervical cord uptake > liver and multifocal/diffuse uptake > liver. SUVmax ratios of conus/liver, conus/left atrium and conus/cervical cord were compared between 3D IR and AdvRecon datasets.

RESULTS

Cauda equina uptake was seen in 64% and 78% on 3D IR and AdvRecon; posterior fossa uptake was seen in 52% and 54% on 3D IR and AdvRecon, respectively. Twelve percent had cauda equina or posterior fossa uptake visible only on AdvRecon. On 3D IR, normal spinal cord uptake was most common (27%); on AdvRecon, conus and cervical cord uptake > liver was most common (32%). Seven of 11 patients with normal spinal cord uptake on 3D IR were upgraded to increased uptake on AdvRecon. AdvRecon showed significantly higher conus/liver, conus/blood pool and conus/cervical cord SUVmax ratios (P < 0.0001).

CONCLUSION

Abnormal uptake in cauda equina, posterior fossa and spinal cord uptake are visible on FDG PET in leptomeningeal disease with increased conspicuity advanced PET reconstructions.

FDG PET in Diffuse Spinal Carcinomatous Meningitis

A 65-year-old man, diagnosed with right paranasal sinus neuroendocrine carcinoma with skull base invasion and ipsilateral lymph node involvement underwent chemotherapy. Six months later, the patient underwent radiation therapy for right cervical lymph node recurrence. Two months after the end of the radiation therapy, the patient was referred to our department to perform a whole-body FDG PET for therapeutic assessment. It showed diffuse intense FDG uptake of the whole spinal canal. The physical examination revealed walking disorders. Meningeal contrast enhancement on MRI of the brain and the spinal cord was leading to the diagnosis of carcinomatous meningitis.

Leptomeningeal carcinomatosis in patients with breast cancer

Leptomeningeal carcinomatosis (LC) is defined as infiltration of the leptomeninges by metastatic carcinoma, a relatively uncommon but devastating complication of many malignancies. Although only 5% of patients with breast cancer develop leptomeningeal involvement, it remains the most common etiology of LC. It can occur as a late-stage complication of systemic progression or present as the first sign of metastatic disease, with or without parenchymal brain metastases. Lobular carcinomas have a higher propensity to metastasize into the meninges when compared to ductal carcinoma, especially the triple-negative subtype, which usually is associated with a shorter interval between metastatic breast cancer diagnosis and the development of LC. Prognosis remains poor, with median survival of 4 months for patients receiving state-of-the-art treatment. The main factors associated with survival are performance status at diagnosis, CSF protein level and triple-negative subtype. Headache is commonly the first clinical presentation of LC, and the diagnostic workup usually requires CSF-cytological analysis and or/MRI. The current management of LC consists of a combination of intra-CSF chemotherapy, systemic therapy, radiotherapy and/or best-supportive care. The standard intra-CSF chemotherapy regimen is methotrexate. Radiotherapy is used for relieving obstruction points on CSF-outflow channels due to ependymal nodules, tumor deposits or bulky disease. Objective responses have been reported with intrathecal administration of trastuzumab for HER2-positive disease, yet this strategy is still under investigation. Further prospective trials are needed to better address the impact of these treatment modalities on overall survival and quality of life.