Overview of treatment strategies in paraneoplastic neurological syndromes

Treatment strategies in paraneoplastic neurological syndromes rely on the three pillars of tumor treatment, immunotherapy, and symptomatic treatment, the first one being by far the most important in the majority of patients and syndromes. Classically, antibodies against extracellular antigens are directly pathogenic, and patients with these syndromes are more responsive to immunomodulatory or immunosuppressive treatments than the ones with antibodies against intracellular targets. This chapter first discusses some general principles of tumor treatment and immunotherapy, followed by a closer look at specific treatment options for different clinical syndromes, focusing on symptomatic treatments.

Neurological Manifestations of Scrub Typhus

PURPOSE OF REVIEW

The occurrence of cases of scrub typhus is on the rise in South Asian and Southeast Asian countries. The present review discusses neurological complications following scrub typhus to appraise clinicians practicing in endemic regions about considering this treatable disease in the differential diagnosis of acute febrile illnesses, especially when accompanied with clinical neurological features.

RECENT FINDINGS

While the association of aseptic meningitis, encephalitis, and meningoencephalitis with scrub typhus is well known, more recently described neurological syndromes associated with scrub typhus include acute disseminated encephalomyelitis, various cranial nerve palsies, cerebellitis, cerebrovascular diseases including cerebral venous sinus thrombosis, transverse myelitis, longitudinally extensive transverse myelitis, Guillain-Barré syndrome, opsoclonus-myoclonus syndrome, parkinsonism, and many more. Early diagnosis is key to successful treatment. While diagnostic confirmation is generally made by the detection of IgM antibody by either ELISA or indirect fluorescent antibody tests, conventional PCR using 56 kDa gene (cPCR) and loop-mediated isothermal amplification assay (LAMP assay), as well as a newly introduced metagenomic next-generation sequencing (mNGS), are currently available for detection of Orientia tsutsugamushi infection in clinically suspected cases. Scrub typhus is an acute febrile illness caused by Orientia tsutsugamushi. The cutaneous hallmark of the disease is the "eschar." Scrub typhus results in multisystem involvement. Neurological compromise is present in about 20% of scrub typhus patients and affects both the central nervous system and the peripheral nervous system. The postulated underlying mechanisms include direct invasion of the organism, a vasculitis-like process, or an immune-mediated injury. Diagnosis of scrub typhus is confirmed by detection of O. tsutsugamushi IgM antibody in serum. Awareness among clinicians regarding the varied presentations of this disease is very important in order to reduce morbidity and mortality. Co-infection with dengue and/or chickungunya viruses may occur in endemic regions. The history of an acute febrile illness preceding the neurological illness is crucial. A very careful search for the eschar is essential; however, the absence of the skin lesion cannot exclude the diagnosis of scrub typhus. Neurological manifestations mostly respond to doxycycline therapy.

Paraneoplastic syndromes in ophthalmology

Paraneoplastic syndromes consist on systemic manifestations associated with certain cancers which are not a direct consequence of tumor invasion or its metastases. It is known that autoimmunity and autoantibody synthesis play an important role in its pathophysiology due to a process of molecular mimicry. Paraneoplastic syndromes in ophthalmology are rare, but it is important to recognize them clinically because in some cases symptoms preceded the diagnosis of an underlying neoplasia. Most frequently involved cancer is small cell lung carcinoma, but there is also a relationship with other tumor etiologies such as thymoma, gynecological tumors or neuroblastoma in children. Paraneoplastic syndromes with ocular involvement can be divided into those that affect the afferent visual pathway, such as cancer-associated retinopathy, melanoma-associated retinopathy, or paraneoplastic optic neuropathy; and the ones that affect the efferent visual pathway, such as bilateral tonic pupils, Myasthenia Gravis, Lambert-Eaton syndrome or paraneoplastic cerebellar degeneration. The presence of autoantibodies is helpful in clinical practice but negativity does not exclude this diagnosis. Although evolution and prognosis is linked to primary disease, in some cases specific treatment, usually immunosuppressive therapy, can help improving patients quality of life.

Immunoproteomic studies on paediatric opsoclonus-myoclonus associated with neuroblastoma

We aimed to identify new cell-membrane antigens implicated in opsoclonus-myoclonus with neuroblastoma. The sera of 3 out of 14 patients showed IgG electron-microscopy immunogold reactivity on SH-SY5Y neuroblastoma cells. Immunoprecipitation experiments using rat brain synaptosomes and SH-SY5Y cells led to the identification of: (1) thirty-one nuclear/cytoplasmic proteins (including antigens HuB, HuC); (2) seven neuronal membrane proteins, including the Shaw-potassium channel Kv3.3 (KCNC3), whose genetic disruption in mice causes ataxia and generalized muscle twitching. Although cell-based assays did not demonstrate direct antigenicity, our findings point to Shaw-related subfamily of the potassium voltage-gated channels complexed proteins as hypothetical antigenic targets.