Response to heat pain stimulation in idiopathic Parkinson's disease

BACKGROUND

Pain is a prominent nonmotor symptom in Parkinson's disease (PD) but has not been well studied.

OBJECTIVE

The aim of this study is to assess thermal experience and emotional content, as well as side-to-side sensory differences in PD "off" and "on" dopaminergic therapy following thermal cutaneous stimulation.

DESIGN

Cross-sectional design.

SETTING

University teaching hospital.

METHODS

Twelve PD subjects experiencing motor fluctuations but no pain symptoms and 13 healthy controls participated in the study. Heat pain and emotional content were assessed using a thermode and visual analog scales in medication on and off states in PD and without medication in healthy controls.

RESULTS

There were no side to side differences in heat pain intensity or between PD medication on state and PD medication off state. Unexpectedly, PD subjects reported a higher degree of unpleasantness in response to heat pain while on medication compared with the off state.

CONCLUSIONS

These results suggest that the perception of heat pain is mediated, at least in part, by nondopaminergic systems in PD, while dopamine might modulate the affective component of pain.

Necrotizing vacuolar myopathy presenting with recurrent myoglobinuria

Myoglobinuria occurs in a variety of systemic and neurological disorders and can pose diagnostic challenges. We report on a 23-year-old man in whom recurrent myoglobinuria was observed due to necrotizing vacuolar myopathy confirmed on muscle biopsy. Histopathologically the intramuscular vacuoles lacked the typical findings reported in vacuolar myopathy due to disorders of glycogen and lipid metabolism. We discuss the management approach to recurrent myoglobinuria. Recurrent myoglobinuria in the absence of toxin or drug exposure and seizure is more often due to primary muscle disease. Recognizing the presence of myoglobinuria and the proximate cause is essential in preventing the development of renal dysfunction and the future recurrence of symptoms.

Neuromyelitis optica: an overview

Neuromyelitis optica (NMO) is a relapsing inflammatory disorder of the central nervous system that closely resembles multiple sclerosis. This review discusses recent understanding of NMO with reference to epidemiology, clinical spectrum, immunopathology, diagnostic evaluation, clinical course and management. Within the clinical spectrum of NMO, the classical form (with relapsing opticomyelitis) and limited forms (either recurrent myelitis or optic neuritis), as well as its association with other autoimmune disorders, have been recognised in recent years. Further, symptomatic or asymptomatic cerebral lesions may be present, and such brain lesions do not necessarily exclude the diagnosis. In the appropriate clinical context, the diagnosis is supported by longitudinally extensive myelitis on spinal MRI. Overwhelming evidence strongly indicates that aquaporin 4 antibody has a pathogenetic role in the development of NMO and serves as a useful diagnostic and prognostic marker. Detection of this autoantibody has led to the categorisation of NMO as an autoimmune channelopathy. NMO can be distinguished from multiple sclerosis by a combination of clinical, radiological and laboratory studies. However, the nosological position of Asian opticospinal multiple sclerosis is not settled. In NMO, acute attacks usually result in moderate to severe functional impairment, and, in the absence of a secondary progressive course (unlike relapsing-remitting multiple sclerosis), prevention of relapses is of crucial importance in the management of the disease. Indeed, relapse prevention with long-term immunosuppressive medication remains the cornerstone of therapy in this otherwise debilitating disease!

Progression of dopaminergic dysfunction in a LRRK2 kindred: a multitracer PET study

OBJECTIVE

Little is known about the progression of dopaminergic dysfunction in LRRK2-associated Parkinson disease (PD). We sought to characterize the neurochemical progression with multitracer PET in asymptomatic members of parkinsonian kindred (family D, Western Nebraska) carrying LRRK2 (R1441C) mutation.

METHOD

Thirteen family D subjects underwent PET scans of presynaptic dopaminergic integrity and five subjects were rescanned 2 to 3 years later.

RESULTS

In subjects 8, 9 (mutation carriers), and 13 (genealogically at risk subject), there was a decline in PET markers over the course of the study that was significantly greater than the expected rate of decline in healthy controls. Reduced dopamine transporter binding was the earliest indication of subclinical dopaminergic dysfunction and progression to clinical disease was generally associated with the emergence of abnormal fluorodopa uptake.

CONCLUSION

PET study of presymptomatic members of our LRRK2 kindred revealed dopaminergic dysfunction that progressed over time. This represents an ideal group to study the natural history of early disease and the potential effects of neuroprotective interventions.

Functional imaging in Parkinson disease

OBJECTIVE

Functional imaging techniques represent useful tools to assess in vivo the neurochemical alterations and functional connectivity in Parkinson disease (PD). Here, the authors review the various approaches and potential application of these imaging techniques to the study of PD.

METHOD

Radiotracer imaging using dopaminergic markers facilitates assessment of pre- and postsynaptic nigrostriatal integrity, while imaging with other appropriate radiotracers explores nondopaminergic neurotransmitter function, local metabolism, blood flow, and mechanisms potentially related to disease progression and pathogenesis. Activation studies using functional MRI detect blood oxygen level dependent signal, as an indirect marker of neuronal activity.

RESULT

Functional imaging techniques have been applied to infer the potential role of inflammation and other factors in etiopathogenesis as well as to study compensatory and regulatory mechanisms in early PD and subclinical disease in genetic forms of PD. Imaging studies also help to understand the neurobiological basis of motor and nonmotor complications. Recent reports suggest a role for striatal dopaminergic transmission in modulating neurobehavioral processes including the placebo effect in PD. Although functional imaging has been employed to monitor disease progression, the discordance between clinical outcome and imaging measures after therapeutic interventions precludes their use as surrogate end points in clinical trials. Beyond these limitations and potential challenges, imaging techniques continue to find wide application in the study of PD.

CONCLUSION

Functional imaging can provide meaningful insights into mechanisms underlying various aspects of motor and nonmotor dysfunction in Parkinson disease and the role of striatal dopaminergic transmission in behavioral processes beyond motor control. These modalities hold promise to study the preclinical phase and to elucidate further the benefits and complications of surgical interventions and the utility of neuroprotective strategies.

Generalised convulsive status epilepticus: an overview

Generalised convulsive status epilepticus is one of the most common emergencies encountered in clinical practice. This review discusses the recent understanding of this life-threatening condition with reference to the definition, pathophysiology, evaluation, complications, refractory status and prognosis. Besides epilepsy, other neurological and medical illnesses could be associated with status epilepticus. The goals of management and pharmacological approach are outlined, considering the available evidence. Prompt recognition and timely intervention, including pre-hospital treatment, are therapeutically beneficial. Refractory status should be managed in intensive care units under close monitoring. More evidence is needed for evolving the optimal treatment. A suitable treatment protocol would guide in avoiding the pitfalls at various points along the management pathway.