The nature of progression in Parkinson's disease: an application of non-linear, multivariate, longitudinal random effects modelling

Background

To date, statistical methods that take into account fully the non-linear, longitudinal and multivariate aspects of clinical data have not been applied to the study of progression in Parkinson’s disease (PD). In this paper, we demonstrate the usefulness of such methodology for studying the temporal and spatial aspects of the progression of PD. Extending this methodology further, we also explore the presymptomatic course of this disease.

Methods

Longitudinal Positron Emission Tomography (PET) measurements were collected on 78 PD patients, from 4 subregions on each side of the brain, using 3 different radiotracers. Non-linear, multivariate, longitudinal random effects modelling was applied to analyze and interpret these data.

Results

The data showed a non-linear decline in PET measurements, which we modelled successfully by an exponential function depending on two patient-related covariates duration since symptom onset and age at symptom onset. We found that the degree of damage was significantly greater in the posterior putamen than in the anterior putamen throughout the disease. We also found that over the course of the illness, the difference between the less affected and more affected sides of the brain decreased in the anterior putamen. Younger patients had significantly poorer measurements than older patients at the time of symptom onset suggesting more effective compensatory mechanisms delaying the onset of symptoms. Cautious extrapolation showed that disease onset had occurred some 8 to 17 years prior to symptom onset.

Conclusions

Our model provides important biological insights into the pathogenesis of PD, as well as its preclinical aspects. Our methodology can be applied widely to study many other chronic progressive diseases.

Treatable Neuropsychiatric Syndrome of Catatonia: A Case Review from Oman

Catatonia is a potentially treatable neuropsychiatric syndrome less commonly encountered in developed countries these days. This review presents a case of a 19-year-old male with catatonic signs and symptoms compounded within a spectrum of a mood disorder, as well as literature review of the current treatment guidelines for this condition. There was no structural brain lesion or abnormality on cranial magnetic resonance imaging. The patient demonstrated favorable therapeutic response to benzodiazepine. This report discusses the management approach for catatonia through the case illustration, in an attempt to improve awareness and prompt recognition of this important disorder among physicians in Oman.

Acute drug overdose: clinical profile, etiologic spectrum and determinants of duration of intensive medical treatment

OBJECTIVES

Acute drug overdosing is an important cause of organ dysfunction and metabolic derangements and the patients often require intensive care. This study aims to determine the clinical pattern of severe drug overdose as well as the factors influencing the duration of intensive care

METHODS

The clinical characteristics and course of consecutive adult patients admitted with a diagnosis of acute drug poisoning in the ICU of a tertiary hospital in Oman from January 2007 to December 2008 were reviewed retrospectively from the electronic case records.

RESULTS

Acute drug poisoning (n=29) constituted 3.9% of admissions to the ICU. Mean age was 29.38±7.9 years. They were brought in by their relatives (72%) or the state services (24%). Accidental poisoning was noted in 21 patients (72%) and suicidal overdosing in 6 (21%). The commonest drug was an opioid (65.5%). Glasgow Coma Scale score of ≤8 was recorded in 18 (62.1%). Sixty two percent of patients required mechanical ventilation. The prominent complications were hypotension in 9 (31%), pulmonary in 19 (65.5%), hepatic in 18 (62.1%) and renal in 12 (41.4%) patients. The major electrolytes abnormalities were low bicarbonate in 11 (37.9%), hyponatremia in 5 (17.2%) and hypokalemia in 4 (13.8%). Patients stayed in the ICU for 1 to 20 days (median-2 days). Factors associated with a longer ICU stay included hypotension upon arrival (p=0.048) and the need for mechanical ventilation on the first (p=0.001) and second (p=0.001) days of hospitalization. There was no mortality.

CONCLUSION

Early and prompt intensive medical therapy in acute drug poisoning can favorably influence the outcome. In addition, the presence of hypotension and requirement of mechanical ventilation on the first two days of hospitalization were responsible for prolonged ICU stay.

Full Outline of UnResponsiveness score and Glasgow Coma Scale in medical patients with altered sensorium: interrater reliability and relation to outcome

PURPOSE

Full Outline of UnResponsiveness, or FOUR score (FS), is a recently described scoring system for evaluation of altered sensorium. This study examined interrater reliability for FS and Glasgow Coma Scale (GCS) among medical patients with altered mental status and compared outcome predictability of GCS, FS, and Sequential Organ Failure Assessment score.

PATIENTS AND METHODS

Adult patients with altered mental status due to medical causes were rated by neurology consultants and internal medicine residents on FS and GCS. Interobserver reliability for GCS and FS was assessed using κ score. Relation with outcomes was explored using univariate and multivariate analyses.

MAIN RESULTS

Of the 100 patients (age, 62 ± 17 years), 60 had neurologic conditions; 26, metabolic encephalopathy; 9, infections; and 7, others. Thirty-nine patients died at 3 months. κ Scores ranged from 0.71 to 0.85 for GCS and from 0.71 to 0.95 for FS. On multivariate analysis, GCS was predictive of outcome at 3 months; FS was predictive of mortality. Area under the receiver operating characteristic curves suggested equivalent performance of both scoring systems.

CONCLUSIONS

Interrater reliability and outcome predictability for FS were comparable with those for GCS. This study supports the use of FS for evaluation of altered mental status in the medical wards.

Misdiagnosis of Myasthenia Gravis and Subsequent Clinical Implication: A case report and review of literature

The autoimmune disease, myasthenia gravis (MG), can mimic a variety of neurological disorders leading to a delay in diagnosis and treatment. On occasions, misdiagnosis of MG could lead to unnecessary and potentially harmful therapeutic interventions. We report on a 12 year-old boy, in whom MG was mistaken for meningitic sequelae and subsequently for critical neuropathy/myopathy resulting in considerable morbidity for nearly a decade. Subsequent correct diagnosis and optimal management resulted in significant improvement in his functional status. We discuss the importance of considering MG as one of the potential differential diagnoses among cases of recurrent respiratory pump failure, or unexplained bulbar symptoms where documentary proof of the previous diagnoses including work-up for MG is lacking. We also review the literature on MG misdiagnosis and highlight the potential pitfalls in MG diagnosis.

Longitudinal evolution of compensatory changes in striatal dopamine processing in Parkinson's disease

Parkinson's disease is a relentlessly progressive neurodegenerative disease. Breakdown of compensatory mechanisms influencing putaminal dopamine processing could contribute to the progressive motor symptoms. We studied a cohort of 78 subjects (at baseline) with sporadic Parkinson's disease and 35 healthy controls with multi-tracer positron emission tomography scans to investigate the evolution of adaptive mechanisms influencing striatal dopamine processing in Parkinson's disease progression. Presynaptic dopaminergic integrity was assessed with three radioligands: (i) [(11)C](±)dihydrotetrabenazine, to estimate the density of vesicular monoamine transporter type 2; (ii) [(11)C]d-threo-methylphenidate, to label the dopamine transporter; and (iii) 6-[(18)F]fluoro-L-DOPA, to assess the activity of aromatic amino acid decarboxylase and storage of 6-[(18)F]-fluorodopamine in synaptic vesicles. The subjects with Parkinson's disease and the healthy controls underwent positron emission tomography scans at the initial visit and after 4 and 8 years of follow-up. Non-linear multivariate regression analyses with random effects were utilized to model the longitudinal changes in tracer values in the putamen standardized relative to normal controls. We found evidence for possible upregulation of dopamine synthesis and downregulation of dopamine transporter in the more severely affected putamen in the early stage of Parkinson's disease. The standardized 6-[(18)F]fluoro-L-DOPA and [(11)C]d-threo-methylphenidate values tended to approach [(11)C](±)dihydrotetrabenazine values in the putamen in later stages of disease (i.e. for [(11)C](±)dihydrotetrabenazine values <25% of normal), when the rates of decline in the positron emission tomography measurements were similar for all the markers. Our data suggest that compensatory mechanisms decline as Parkinson's disease progresses. This breakdown of compensatory strategies in the putamen could contribute to the progression of motor symptoms in advanced disease.

Callosal warning syndrome

OBJECTIVE

To report the clinical and imaging findings in a patient with an initial fluctuating disconnection syndrome due to corpus callosal ischemia that ultimately culminated in infarction with persistent symptoms.

CASE REPORT

A 40-year-old, hypertensive, right-handed man presented with transient, stereotyped symptoms of corpus callosal disconnection (intermanual conflict, apraxia, dysgraphia and construction difficulties in his left hand). Serial magnetic resonance imaging scans demonstrated the ischemic nature of the initial fluctuating symptoms and later showed callosal infarction when the symptoms were persistent. Magnetic resonance angiogram did not reveal significant stenosis or occlusion of the internal carotid or proximal portion of anterior cerebral arteries. Patient received standard treatment for ischemic stroke and at follow-up 1 month later, had mild left hand apraxia, dysgraphia and construction difficulties.

CONCLUSION

The case highlights the unusual occurrence of crescendo transient ischemic attacks culminating in infarction in the location of corpus callosum. We have termed this novel stroke syndrome as 'callosal warning syndrome' as the temporal profile was quite indistinguishable from that of relatively well-known stroke warning syndromes in the location of internal capsule and pontine tegmentum.

Dopamine turnover increases in asymptomatic LRRK2 mutations carriers

Increase in dopamine (DA) turnover was found to occur early in symptomatic Parkinson's disease (PD) and to be functionally related to the dopamine transporter (DAT). The objectives of this study were to examine changes in DA turnover in the asymptomatic PD phase; to compare them with changes in other dopaminergic markers, and to investigate a possible relationship between DAT and DA turnover. Eight subjects from families at increased risk of PD due to LRRK2 mutation were investigated. Positron emission tomography imaging was performed with: ¹⁸F-fluorodopa to determine the effective DA distribution volume (EDV), the inverse of DA turnover, and the DA uptake rate K(occ), a marker of DA synthesis and storage; ¹¹C-methylphenidate (MP, a DAT marker) and ¹¹C-dihydrotetrabenazine (DTBZ, a VMAT2 marker) to estimate the binding potentials BP(ND_MP) and BP(ND_DTBZ). On average, EDV showed the largest reduction from age-matched control values (42%) followed by BP(ND_MP) (23%) and BP(ND_DTBZ) (17%), whereas K(occ) remained in the normal range for all subjects. No correlation was found between EDV and any other marker. DA turnover was found to be elevated in asymptomatic mutation carriers at increased risk of PD. Such change was determined to be larger than and statistically independent from changes observed with the other markers. These results support a compensatory role of increased DA turnover in presymptomatic disease and indicate that at this stage, in contrast to the symptomatic PD phase, increased turnover is not related to DAT.

Spinal Cord Infarction following Abdominal Surgery and Postoperative Epidural Analgaesia

Ischemic infarction is a rare cause of acute myelopathy. We report the case of a young woman admitted to Sultan Qaboos University Hospital, Oman, who developed extensive spinal cord infarction in the setting of surgical evacuation and packing of liver haematoma and post-operative epidural analgesia. She had no vascular risk factors for stroke. The vascular mechanism underlying ischemic myelopathy and the relationship to abdominal surgery and epidural analgesia are discussed.