Changes in the thalamus in atypical parkinsonism detected using shape analysis and diffusion tensor imaging.

BACKGROUND AND PURPOSE: The thalamus is interconnected with the nigrostriatal system and cerebral cortex and has a major role in cognitive function and sensorimotor integration. The purpose of this study was to determine how regional involvement of the thalamus differs among Parkinson disease, progressive supranuclear palsy, and corticobasal syndrome. MATERIALS AND METHODS: Nine patients with Parkinson disease, 5 with progressive supranuclear palsy, and 6 with corticobasal syndrome underwent 3T MR imaging along with 12 matched, asymptomatic volunteers by using a protocol that included volumetric T1 and diffusion tensor imaging. Acquired data were automatically processed to delineate the margins of the motor and nonmotor thalamic nuclear groups, and measurements of ADC were calculated from the DTI data within these regions. Thalamic volume, shape, and ADC were compared across groups. RESULTS: Thalamic volume was smaller in the progressive supranuclear palsy and corticobasal syndrome groups compared with the Parkinson disease and control groups. Shape analysis revealed that this was mainly due to the diminished size of the lateral thalamus. Overall, ADC measurements were higher in the progressive supranuclear palsy group compared with both the Parkinson disease and control groups, and anatomic subgroup analysis demonstrated that these changes were greater within the motor regions of the thalamus in progressive supranuclear palsy and corticobasal degeneration. CONCLUSIONS: Reduced size and increased ADC disproportionately involve the lateral thalamus in progressive supranuclear palsy and corticobasal syndrome, consistent with selective neurodegeneration and atrophy in this region. Because these findings were not observed in Parkinson disease, they may be more specific markers of tau-related neurodegeneration.

Fall frequency and risk assessment in early Parkinson's disease.

BACKGROUND: We sought to define the frequency of falls in early PD and assess potential risk factors for falls in this population. METHODS: We analyzed the data from two randomized, placebo controlled trials (NET-PD FS1 and FS-TOO) of 413 individuals with early PD over 18 months of follow-up in FS1 and 12 months in FS-TOO. Falls were defined as any report of falls on the UPDRS or the adverse event log. We assessed the frequency of falls overall and by age. The relationship between prespecified fall risk markers and the probability of falling was assessed using logistic and multiple logistic regression. A hurdle Poisson model was used to jointly model the probability of remaining fall-free and the number of falls. RESULTS: During the follow-up period, 23% of participants fell, and 11% were habitual fallers. In a multiple logistic regression model, age, baseline UPDRS Falling score, and baseline PDQ-39 scores were associated with subsequent fall risk (p < 0.001). Similarly, in a hurdle Poisson regression model, age, baseline UPDRS falling item, and baseline PDQ-39 were all significantly related to the probability of falling, but only UPDRS falling >0 was associated with the number of falls. CONCLUSION: Falls are frequent and are associated with impaired quality of life, even in early PD. Current standard rating scales do not sufficiently explain future fall risk in the absence of a prior fall history. New assessment methods for falls and postural instability are required to better evaluate this important problem in clinical trials and clinical practice.

Trends in American Board of Psychiatry and Neurology specialties and neurologic subspecialties.

OBJECTIVE: To review the current status and recent trends in the American Board of Psychiatry and Neurology (ABPN) specialties and neurologic subspecialties and discuss the implications of those trends for subspecialty viability. METHODS: Data on numbers of residency and fellowship programs and graduates and ABPN certification candidates and diplomates were drawn from several sources, including ABPN records, Web sites of the Accreditation Council for Graduate Medical Education and the American Medical Association, and the annual medical education issues of the Journal of the American Medical Association. RESULTS: About four-fifths of neurology graduates pursue fellowship training. While most recent neurology and child neurology graduates attempt to become certified by the ABPN, many clinical neurophysiologists elect not to do so. There appears to have been little interest in establishing fellowships in neurodevelopmental disabilities. The pass rate for fellowship graduates is equivalent to that for the "grandfathers" in clinical neurophysiology. Lower percentages of clinical neurophysiologists than specialists participate in maintenance of certification, and maintenance of certification pass rates are high. CONCLUSION: The initial enthusiastic interest in training and certification in some of the ABPN neurologic subspecialties appears to have slowed, and the long-term viability of those subspecialties will depend upon the answers to a number of complicated social, economic, and political questions in the new health care era.

Safety and tolerability of putaminal AADC gene therapy for Parkinson disease.

BACKGROUND: In Parkinson disease (PD), the benefit of levodopa therapy becomes less marked over time, perhaps because degeneration of nigrostrial neurons causes progressive loss of aromatic l-amino acid decarboxylase (AADC), the enzyme that converts levodopa into dopamine. In a primate model of PD, intrastriatal infusion of an adeno-associated viral type 2 vector containing the human AADC gene (AAV-hAADC) results in robust response to low-dose levodopa without the side effects associated with higher doses. These data prompted a clinical trial. METHODS: Patients with moderately advanced PD received bilateral intraputaminal infusion of AAV-hAADC vector. Low-dose and high-dose cohorts (5 patients in each) were studied using standardized clinical rating scales at baseline and 6 months. PET scans using the AADC tracer [(18)F]fluoro-L-m-tyrosine (FMT) were performed as a measure of gene expression. RESULTS: The gene therapy was well tolerated, but 1 symptomatic and 2 asymptomatic intracranial hemorrhages followed the operative procedure. Total and motor rating scales improved in both cohorts. Motor diaries also showed increased on-time and reduced off-time without increased "on" time dyskinesia. At 6 months, FMT PET showed a 30% increase of putaminal uptake in the low-dose cohort and a 75% increase in the high-dose cohort. CONCLUSION: This study provides class IV evidence that bilateral intrastriatal infusion of adeno-associated viral type 2 vector containing the human AADC gene improves mean scores on the Unified Parkinson's Disease Rating Scale by approximately 30% in the on and off states, but the surgical procedure may be associated with an increased risk of intracranial hemorrhage and self-limited headache.

Recommendations for the clinical use of somatosensory-evoked potentials.

The International Federation of Clinical Neurophysiology (IFCN) is in the process of updating its Recommendations for clinical practice published in 1999. These new recommendations dedicated to somatosensory-evoked potentials (SEPs) update the methodological aspects and general clinical applications of standard SEPs, and introduce new sections dedicated to the anatomical-functional organization of the somatosensory system and to special clinical applications, such as intraoperative monitoring, recordings in the intensive care unit, pain-related evoked potentials, and trigeminal and pudendal SEPs. Standard SEPs have gained an established role in the health system, and the special clinical applications we describe here are drawing increasing interest. However, to prove clinically useful each of them requires a dedicated knowledge, both technical and pathophysiological. In this article we give technical advice, report normative values, and discuss clinical applications.

Results from a phase I safety trial of hAADC gene therapy for Parkinson disease.

BACKGROUND: In a primate model of Parkinson disease (PD), intrastriatal infusion of an adeno-associated viral (AAV) vector containing the human aromatic l-amino acid decarboxylase (hAADC) gene results in robust gene expression. After gene transfer, low doses of systemically administered l-dopa are converted to dopamine in the transduced striatal neurons, resulting in behavioral improvement without the side effects typically associated with higher doses of l-dopa. These studies led to the initiation of a phase I safety trial. Here we report the findings for the first cohort of five patients. METHODS: Patients with moderate to advanced PD received bilateral infusion of a low dose of the AAV-hAADC vector into the putamen. PET scans using the AADC tracer, 6-[18F]fluoro-l-m-tyrosine (FMT), were performed at baseline and at 1 and 6 months after infusion as an in vivo measure of gene expression. RESULTS: PET results showed an average 30% increase in FMT uptake (K(i)(c)) in the putamen after gene transfer. Preliminary analysis of clinical data indicates a modest improvement, but absence of a control and the nonblinded analyses make interpretation difficult. CONCLUSIONS: Thus far, this gene therapy approach has been well tolerated and shows PET evidence of sustained gene expression. These initial findings demonstrate the safety of the therapy; higher doses of adeno-associated viral vector containing the human aromatic l-amino acid decarboxylase gene in the next cohort of patients may further increase dopamine production in the putamen and provide more profound clinical benefit.

Reporting clinical trials: full access to all the data.

Authors' right to access to all data obtained in their study

The Brown-Séquard and S. Weir Mitchell letters.

The two prominent nineteenth-century neurophysiologists/neurologists C.E. Brown-Séquard and S.W. Mitchell maintained an active correspondence during their careers. These letters, never before studied as a unit, provide insight into the men's close collegial association in several domains. They shared camaraderie as pioneer physiologists who tried to bring experimental discoveries from the laboratory to the clinical setting. They critiqued each other's research and facilitated its publication in journals over which they had influence. Through letters of recommendation, they also helped foster each other's local careers. In a period of transition in neuroscience from a traditional anatomic focus to the emerging predominance of neurophysiology and neuropharmacology, their correspondence documents the views of two late nineteenth-century leaders in science and international academic medicine.

Cubilin dysfunction causes abnormal metabolism of the steroid hormone 25(OH) vitamin D(3).

Steroid hormones are central regulators of a variety of biological processes. According to the free hormone hypothesis, steroids enter target cells by passive diffusion. However, recently we demonstrated that 25(OH) vitamin D(3) complexed to its plasma carrier, the vitamin D-binding protein, enters renal proximal tubules by receptor-mediated endocytosis. Knockout mice lacking the endocytic receptor megalin lose 25(OH) vitamin D(3) in the urine and develop bone disease. Here, we report that cubilin, a membrane-associated protein colocalizing with megalin, facilitates the endocytic process by sequestering steroid-carrier complexes on the cellular surface before megalin-mediated internalization of the cubilin-bound ligand. Dogs with an inherited disorder affecting cubilin biosynthesis exhibit abnormal vitamin D metabolism. Similarly, human patients with mutations causing cubilin dysfunction exhibit urinary excretion of 25(OH) vitamin D(3). This observation identifies spontaneous mutations in an endocytic receptor pathway affecting cellular uptake and metabolism of a steroid hormone.

Parkinson's disease.

A number of changes have occurred in the management of Parkinson's disease in recent years, with the development of new therapeutic strategies based upon advances in pharmacotherapy and interventional procedures. The treatment of patients with Parkinson's disease is considered here with these advances in mind. Potential neuroprotective agents that might slow disease-progression are also considered, but at the present time these agents are more of academic interest than clinical relevance and their role remains to be established. Ablative surgery and stimulation procedures are also helpful in the management of Parkinson's disease, and the utility and limitations of these approaches are briefly summarized.

Cubilin P1297L mutation associated with hereditary megaloblastic anemia 1 causes impaired recognition of intrinsic factor-vitamin B(12) by cubilin.

Megaloblastic anemia 1 (MGA1) is an autosomal recessive disorder caused by the selective intestinal malabsorption of intrinsic factor (IF) and vitamin B(12)/cobalamin (Cbl) in complex. Most Finnish patients with MGA1 carry the disease-specific P1297L mutation (FM1) in the IF-B(12) receptor, cubilin. By site-directed mutagenesis, mammalian expression, and functional comparison of the purified wild-type and FM1 mutant forms of the IF-Cbl-binding cubilin region (CUB domains 5-8, amino acid 928-1386), we have investigated the functional implications of the P1297L mutation. Surface plasmon resonance analysis revealed that the P1297L substitution specifically increases the K(d) for IF-Cbl binding several-fold, largely by decreasing the association rate constant. In agreement with the binding data, the wild-type protein, but not the FM1 mutant protein, potently inhibits 37 degrees C uptake of iodine 125-IF-Cbl in cubilin-expressing epithelial cells. In conclusion, the data presented show a substantial loss in affinity of the FM1 mutant form of the IF-Cbl binding region of cubilin. This now explains the malabsorption of Cbl and Cbl-dependent anemia in MGA1 patients with the FM1 mutation. (Blood. 2000;96:405-409)

Studies of the human stretch reflex.

We recorded the late electromyographic (EMG) responses to predictable and unpredictable stretches of the wrist flexor and extensor muscles during ballistic movement or isometric contractions. We simultaneously recorded the accompanying cerebral responses. Our findings suggest that the late EMG responses are influenced by suprasegmental (cerebral) phasic mechanisms that seem to have a dual functional role, being involved in the control of limb stiffness and in a servomechanism to return the displaced limb to its intended position.

Effect of pallidotomy on postural control and motor function in Parkinson disease.

OBJECTIVE: To investigate the effects of pallidotomy on postural reactions and other motor parkinsonian deficits. DESIGN: Comparison of performance by patients before and after pallidotomy on tests of balance and function. SETTING: A Parkinson disease Center of Excellence and Center for Human Performance Testing at a university hospital and research center. PARTICIPANTS: Twenty-nine patients with Parkinson disease undergoing pallidotomy. MAIN OUTCOME MEASURES: Performance results on the United Parkinson's Disease Rating Scale (UPDRS), activities of daily living and motor subscales (parts II and III). and posturography (sensory organization test), which were collected before and 3 and 6 months after surgery with patients in the practically defined off state (medication withheld for at least 12 hours). RESULTS: Data were analyzed with a paired Wilcoxon and Spearman correlation. There was a significant improvement in mean +/- SD UPDRS motor subscale score after pallidotomy (before surgery, 52.43+/-13.46; after surgery, 43.93+/-15.15; z= 3.63; P=.003). There were no significant changes in the UPDRS activities of daily living subscale or average stability scores when the group was examined as a whole. However, examination of individual data revealed that 9 (56%) of 16 patients who could stand independently before surgery showed improvement in either the number of falls or the average stability score. No patient who was unable to stand independently before surgery was able to stand independently after it. CONCLUSION: Pallidotomy helped improve overall motor function in patients with parkinsonism and, for some patients, also improved postural stability.