Essential Tremor and Essential Tremor Plus Are Essentially Similar Electrophysiologically

BACKGROUND

The merits of classifying the heterogeneous group of essential tremors into essential tremor (ET) and essential tremor plus (ETP) are debated.

OBJECTIVES

We studied the electrophysiological and spiral characteristics of tremor in ET and ETP.

METHODS

We reviewed standardized videos from a tremor database and clinically classified patients into ET, ETP, or dystonic tremor (DT). The following variables were derived from combined tri-axial accelerometry-surface electromyography (EMG)-peak frequency, total power, peak power, full width half maximum, tremor stability index and EMG-coherence. We analyzed hand-drawn spirals to derive mean deviation, tremor variability, inter-, and intra-loop widths. We compared these variables among the groups.

RESULTS

We recruited 72 participants (81.9% male) with mean age 47.7 ± 16.1 years and Fahn-Tolosa-Marin Tremor Rating Scale total score 31.1 ± 14.1. Patients with ET were younger (P = 0.014) and had less severe tremor (P = 0.020) compared to ETP and DT. In ETP group, 48.6% had subtle dystonia. Peak frequency was greater in ETP (7.3 ± 0.3 Hz) compared to DT (6.1 ± 0.4 Hz; P = 0.024). Peak power was greater in ETP and DT for postural tremor. Rest tremor was recordable on accelerometry in 26.7% of ET. Other variables were similar among the groups.

CONCLUSION

Electrophysiological evaluation revealed postural tremor of frequency 6 to 7 Hz in ET, ETP, and DT with subtle differences more severe tremor in ETP and DT, and higher frequency in ETP compared to DT. Our findings suggest a similar tremor oscillator in these conditions, supporting the view that these entities are part of a spectrum of tremor disorders, rather than distinct etiological entities.

Neuropathic Tremor in Guillain-Barré Syndrome

Background

Neuropathic Tremor (NT) is a postural/kinetic tremor of the upper extremity, often encountered in patients with chronic neuropathies such as paraprotein-associated and hereditary neuropathies.

Objectives

To describe the clinical and electrophysiological features of NT in a previously underrecognized setting- during recovery from Guillain-Barré Syndrome (GBS).

Methods

Patients with a documented diagnosis of GBS in the past, presenting with tremor were identified from review of clinical records. Participants underwent structured, videotaped neurological examination, and electrophysiological analysis using tri-axial accelerometry-surface electromyography. Tremor severity was assessed using the Fahn-Tolosa-Marin Tremor Rating Scale.

Results

We describe the clinical and electrophysiological features of 5 patients with GBS associated NT. Our cohort had a fine, fast, and slightly jerky postural tremor of frequency ranging from 8 to 10 Hz. Dystonic posturing and overflow movements were noted in 4/5 patients. Tremor appeared 3 months-5 years after the onset of GBS, when patients had regained near normal muscle strength and deep tendon jerks were well elicitable. Electrophysiological analysis of tremor strongly suggested the presence of a central oscillator in all patients.

Conclusion

NT is not limited to chronic inflammatory or hereditary neuropathies and may occur in the recovery phase of GBS. The tremor is characterized by a high frequency, jerky postural tremor with dystonic posturing. Electrophysiological evaluation suggests the presence of a central oscillator, hypothetically the cerebellum driven by impaired sensorimotor feedback.

Social Cognition in Parkinson's Disease: A Case-Control Study

Background

Social cognition is the study of how people make sense of themselves and others. Impairment in several domains of social cognition is increasingly being recognized in Parkinson's disease (PD).

Objectives

We aimed to study multiple domains of social cognition in Indian PD patients using a culturally appropriate, validated instrument.

Methods

We recruited 52 individuals with PD and 31 healthy volunteers (HV) and used the Social Cognition Rating Tools in Indian Setting (SOCRATIS) tool to assess theory of mind (ToM), attributional biases and social cue perception. Quality of life (QoL) was assessed using the PDQOL scale.

Results

Baseline characteristics were comparable between PD and HV. The mean (SD) FOT index (first order ToM index) was 0.86(0.18) in PD and 0.99(0.07) in HV [P < 0.001]. The PD group showed higher Externalizing Bias [EB, 4.42(3.91)], compared to HV [1.58(3.22), P = 0.001]. The mean (SD) Faux Pas Composite Index (FPCI ALT) was 0.69(0.09) in PD and 0.78(0.13) in HV [P < 0.001]. Social cognition indices were not associated with QoL in PD. Clinical parameters-age, gender, HAM-D, MOCA, education, levodopa equivalent daily dose of medication, number of PD drugs and trihexyphenidyl use did not predict social cognition.

Conclusion

PD patients were less successful than age, gender matched controls in understanding social situations and other's thought processes and had higher tendency to attribute undesirable events to external causes. Deficits in social cognition did not impair the quality of life.

Free-Ranging Dogs Are Capable of Utilizing Complex Human Pointing Cues

Dogs are one of the most common species to be found as pets and have been subjects of human curiosity, leading to extensive research on their socialization with humans. One of the dominant themes in dog cognition pertains to their capacity for understanding and responding to human referential gestures. The remarkable sociocognitive skills of pet dogs, while interacting with humans, is quite well established. However, studies regarding the free-ranging subpopulations are greatly lacking. The interactions of these dogs with humans are quite complex and multidimensional. For the first time, we tested 160 adult free-ranging dogs to understand their ability to follow relatively complex human referential gestures using dynamic and momentary distal pointing cues. We found that these dogs are capable of following distal pointing cues from humans to locate hidden food rewards. However, approximately half of the population tested showed a lack of tendency to participate even after successful familiarization with the experimental setup. A closer inspection revealed that anxious behavioral states of the individuals were responsible for such an outcome. Finally, we compared the results using data from an earlier study with dynamic proximal cues. We found that free-ranging dogs follow distal cues more accurately compared to proximal cue. We assume that life experiences with humans probably shape personalities of free-ranging dogs, which in turn influence their responsiveness to human communicative gestures.