Pharmacological Management of Severe Neuropathic Pain in a Case of Eosinophilic Meningitis Related to Angiostrongylus cantonensis

Ketamine in Severe Leptomeningeal Pain

Carcinomatosis meningitis is a rare but deadly complication of medulloblastoma. Surgical and systemic treatment options are often limited in advanced stages of the cancer. Meningeal irritation from raised intracranial pressure causes leptomeningeal pain that may respond poorly to opioids and common adjuvant analgesics. We present the case of a terminally ill patient with severe leptomeningeal pain that responded to a trial of ketamine as an adjunct to opioids.

Case Report: Angiostrongylus cantonensis Infection Presenting as Small Fiber Neuropathy

Angiostrongylus cantonensis is an emerging parasite that is the most common cause of eosinophilic meningitis worldwide. Human infection typically presents with headache, neck stiffness, and paresthesia. We report a case of a woman with PCR positive A. cantonensis infection who presented with symptoms of small fiber neuropathy (SFN) but no headache. SFN was confirmed by skin biopsy. After failing standard medications for neuropathy, she was treated with intravenous lidocaine with considerable improvement. However, she required medications for 1 year to treat her chronic neuropathy. Infection by A. cantonensis should be added to the list of causes of SFN, and its potential to cause chronic sequelae should be appreciated.

Magnetic resonance imaging in dogs with neuroangiostrongyliasis (rat lungworm disease)

The magnetic resonance imaging (MRI) appearance of the brain and spinal cord in humans with neuroangiostrongyliasis (NA) due to Angiostrongylus cantonensis infection has been well reported. Equivalent studies in animals are lacking. This case series describes clinical and MRI findings in 11 dogs with presumptively or definitively diagnosed NA. MRI of the brain and/or spinal cord was performed using high-field (1.5 T) or low-field (0.25 T) scanners using various combinations of transverse, sagittal, dorsal and three-dimensional (3D) T1-weighted (T1W), transverse, sagittal and dorsal T2-weighted (T2W), T2W fluid-attenuated inversion recovery (FLAIR) and T2*-weighted (T2*W) gradient echo (GRE), dorsal T2W short tau inversion recovery (STIR) and post-gadolinium transverse, sagittal, dorsal and 3D T1W and transverse T2W FLAIR sequences. In 4/6 cases where the brain was imaged, changes consistent with diffuse meningoencephalitis were observed. Evidence of meningeal involvement was evident even when not clinically apparent. The spinal cord was imaged in 9 dogs, with evidence of meningitis and myelitis detected in regions consistent with the observed neuroanatomical localization. Pathognomonic changes of neural larva migrans, as described in some human patients with NA, were not detected. NA should be considered in the differential diagnosis of dogs with MRI evidence of focal or diffuse meningitis, myelitis and/or encephalitis, especially in areas where A. cantonensis is endemic. If not precluded by imaging findings suggestive of brain herniation, cerebrospinal fluid (CSF) collection for cytology, fluid analysis, real-time polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA) testing should be considered mandatory in such cases after the MRI studies.

Further studies of neuroangiostrongyliasis (rat lungworm disease) in Australian dogs: 92 new cases (2010-2020) and results for a novel, highly sensitive qPCR assay

The principal aim of this study was to optimize the diagnosis of canine neuroangiostrongyliasis (NA). In total, 92 cases were seen between 2010 and 2020. Dogs were aged from 7 weeks to 14 years (median 5 months), with 73/90 (81%) less than 6 months and 1.7 times as many males as females. The disease became more common over the study period. Most cases (86%) were seen between March and July. Cerebrospinal fluid (CSF) was obtained from the cisterna magna in 77 dogs, the lumbar cistern in f5, and both sites in 3. Nucleated cell counts for 84 specimens ranged from 1 to 146 150 cells μL-1 (median 4500). Percentage eosinophils varied from 0 to 98% (median 83%). When both cisternal and lumbar CSF were collected, inflammation was more severe caudally. Seventy-three CSF specimens were subjected to enzyme-linked immunosorbent assay (ELISA) testing for antibodies against A. cantonensis; 61 (84%) tested positive, titres ranging from <100 to ⩾12 800 (median 1600). Sixty-one CSF specimens were subjected to real-time quantitative polymerase chain reaction (qPCR) testing using a new protocol targeting a bioinformatically-informed repetitive genetic target; 53/61 samples (87%) tested positive, CT values ranging from 23.4 to 39.5 (median 30.0). For 57 dogs, it was possible to compare CSF ELISA serology and qPCR. ELISA and qPCR were both positive in 40 dogs, in 5 dogs the ELISA was positive while the qPCR was negative, in 9 dogs the qPCR was positive but the ELISA was negative, while in 3 dogs both the ELISA and qPCR were negative. NA is an emerging infectious disease of dogs in Sydney, Australia.

Special Feature: Diagnosis and Treatment of Neuroangiostrongyliasis in Hawai'i

Angiostrongylus cantonensis is a metastrongylid lungworm of rats with a global distribution and the cause of neuroangiostrongyliasis in humans. In Hawai'i, neuroangiostrongyliasis cases have occurred sporadically since 1960; however, in 2001, the number of cases on Maui and Hawai'i Island began to increase significantly. Since most human treatment trials have been conducted in Thailand, where the disease is usually mild, there is a need to develop treatment protocols for Hawai'i, where there is a broader disease spectrum. In 2018, preliminary guidelines for the diagnosis and treatment of neuroangiostrongyliasis were developed for Hawai'i's physicians. This article summarizes those guidelines and provides additional recommendations for individuals who recently ingested an infected intermediate host.

Lidocaine Infusion for Refractory Pain from Rat Lungworm Disease - Honolulu, Hawai'i

Human infection with Angiostrongyloides cantonensis, or rat lungworm disease, manifests most commonly with neurologic symptoms that often include severe diffuse pain. While pain is reported by the majority of patients with rat lungworm disease, there are presently no published guidelines on the approach to pain management for these patients. Here we report a case of rat lungworm disease where severe refractory pain was the most prominent symptom and an intravenous lidocaine infusion was used as a successful treatment modality. Intravenous lidocaine has been shown to be safe and effective in neuropathic pain, refractory cancer pain, and peri-operative pain management. To our knowledge, this is the first case report on the use of lidocaine infusion for the management of refractory pain from rat lungworm disease, and among the first reports of any approach, to pain management for rat lungworm disease. We suggest that a lidocaine infusion protocol be considered when pain from rat lungworm disease fails to respond to first-line analgesics.

Emerging Challenges to the Safe and Effective Use of Methadone for Cancer-Related Pain in Paediatric and Adult Patient Populations

Methadone continues to be an important medication for the treatment of paediatric and adult cancer-related pain. Appropriate patient selection to ensure safe and effective treatment by a team of clinicians who appreciate and are familiar with methadone and its unique pharmacology is crucial. Unlike morphine and other more common opioids, methadone is purported to have involvement with delta-opioid receptor and higher affinity as an N-methyl-D-aspartate-receptor antagonist. Clinically this gives it the advantage of being effective for both nociceptive and neuropathic pain, but also may be useful in the setting of tolerance to other opioids. Methadone also comes in multiple available formulations that can be administrated through a variety of routes beyond the oral route. Challenges with methadone in treating cancer-related pain include drug interactions specifically as it relates to new targeted cancer therapies. Recent guidelines recommend electrocardiogram monitoring with methadone and there is potential for additive cardiac toxicity in the oncology setting. Appropriate dosing of methadone for pain management given age, organ dysfunction, and patients who are on methadone maintenance therapy are also key factors. This article aims to provide clinicians with evidence and clinical practice guidelines for safe and appropriate use of methadone including indication, initiation, and monitoring given its complexity for management of pain in the dynamic oncology setting.