Acute encephalitis in pediatric multisystem inflammatory syndrome associated with COVID-19.

OBJECTIVE: To characterize neurological involvement in multisystem inflammatory syndrome in children (MIS-C) related to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. METHODS: Retrospective analysis of the clinical, electroencephalographic, CSF and neuroradiological parameters recorded in seven children (3 males, aged 3-10 years) affected by MIS-C with acute neurological involvement. RESULTS: All cases presented acute encephalopathy with drowsiness, irritability, mood deflection and diffuse EEG slowing with periodic posterior complexes. Focal neurological signs, normal brain MRI and CSF, were present in four patients; these patients received intravenous methylprednisolone at 30 mg/kg/day for 3 days. In all cases, the clinical picture rapidly improved in the first three days, and all neurological symptoms and EEG abnormalities disappeared within 10 and 30 days respectively. The severity and duration of the EEG abnormalities was proportional to the extent of the neurological involvement. CONCLUSIONS: Patients with MIS-C may present acute encephalitis characterized by rapid-onset encephalopathy and EEG abnormalities (slow wave activity and/or epileptic abnormalities), in some cases associated with focal neurological signs that disappear with immunomodulatory therapy. The detection through neurological evaluation of sentinel neurological signs and distinctive EEG patterns documentable at disease onset will allow timely diagnosis and treatment of these cases.

Holmes' or functional tremor?

OBJECTIVE: Holmes tremor is a rare kind of hyperkinetic movement disorder, clinically characterized by irregular, monolateral, high-amplitude jerks, sharing a quite similar frequency with those observed in Parkinson's disease; its generation likely relies on a combined involvement of cerebello-thalamic and nigrostriatal pathways. METHODS: We report the case of a man with a combined resting-postural-kinetic tremor. Neuroimaging revealed an intracranial dermoid cyst at the right pontocerebellar angle with brainstem dislocation. We performed an extensive electrophysiological assessment from the extensor digitorum communis (EDC) and flexor carpi radialis (FCR) muscles. RESULTS: Both the spontaneous variability of tremor frequency and frequency entrainment argued against an organic aetiology. Polymyography revealed: 1) a paradoxical increase of tremor amplitude with mass loading; 2) jerks' synchronization between antagonistic muscles during voluntary contralateral motor performances; 3) tremor inhibition while asking the patient to make a ballistic movement. CONCLUSIONS: We suggest a complete psychogenic genesis or, at least in part, a possible co-existence of a rubral tremor with functional traits. SIGNIFICANCE: Here, we propose a simple and fast test battery for an early diagnosis of functional tremor. Our results prompt further studies to re-define electrodiagnostic criteria in hyperkinetic movement disorders, possibly updating the floating border between organic and psychogenic disease.

Cerebellar direct current stimulation modulates hand blink reflex: implications for defensive behavior in humans.

The cerebellum is involved in a wide number of integrative functions. We evaluated the role of cerebellum in peripersonal defensive behavior, as assessed by the so-called hand blink reflex (HBR), modulating cerebellar activity with transcranial direct current stimulation (tDCS). Healthy subjects underwent cerebellar (sham, anodal, and cathodal tcDCS) and motor cortex tDCS (anodal or cathodal; 20', 2 mA). For the recording of HBR, electrical stimuli were delivered using a surface bipolar electrode placed on the median nerve at the wrist and EMG activity recorded from the orbicularis oculi muscle bilaterally. Depending on the hand position respective to the face, HBR was assessed in four different conditions: "hand-far," "hand-near" (eyes open), "side hand," and "hand-patched" (eyes closed). While sham and cathodal cerebellar stimulation had no significant effect, anodal tcDCS dramatically dampened the magnitude of the HBR, as measured by the area under the curve (AUC), in the "hand-patched" and "side hand" conditions only, for ipsilateral (F(4,171)  = 15.08, P < 0.0001; F(4,171)  = 8.95, P < 0.0001) as well as contralateral recordings (F(4,171)  = 17.96, P < 0.0001); F4,171)  = 5.35, P = 0.0004). Cerebellar polarization did not modify AUC in the "hand-far" and "hand-near" sessions. tDCS applied over the motor area did not affect HBR. These results seem to support a role of the cerebellum in the defensive responses within the peripersonal space surrounding the face, thus suggesting a possible cerebellar involvement in visual-independent defensive behavior.

Neurophysiological Comparison Among Tonic, High Frequency, and Burst Spinal Cord Stimulation: Novel Insights Into Spinal and Brain Mechanisms of Action.

RATIONALE: Spinal cord stimulation (SCS) is an effective option for neuropathic pain treatment. New technological developments, as high-frequency (HF) and theta burst stimulation (TBS), have shown promising results, although putative mechanisms of action still remain debated. METHODS: thirty patients with lower back pain were enrolled and underwent LF, HF, and TBS. Laser evoked potentials (LEPs) were recorded by using a Nd:YAG laser. Amplitudes and latencies of the main two components (N1, N2/P2) were compared among different experimental sessions. Changes in resting motor threshold (RMT), cortical silent period (cSP), short intracortical inhibition (SICI), and intracortical facilitation (ICF) were also evaluated. RESULTS: TBS dampened LEP amplitudes compared with LF (N1: p = 0.032; N2/P2: p < 0.0001) and HF stimulation (N1: p = 0.029; N2/P2: p < 0.0001, Holm-Sidak post-hoc test). Concurrently, TBS increased N1 latency, when compared with baseline and LF stimulation (p = 0.009 and 0.0033). Whereas RMT and SICI did not change among experimental conditions, TBS significantly prolonged cSP duration compared with baseline (p = 0.002), LF (p = 0.048), and HF-SCS (p = 0.016); finally, both HF (p = 0.004) and TBS (p = 0.0039) increased ICF. CONCLUSION: TBS modulates medial and lateral pain pathways through distinct mechanisms, possibly involving both GABA(a)ergic and Glutamatergic networks at an intracortical level. These results may have implications for therapy and for the choice of best stimulation protocol.

High Hypnotizability Impairs the Cerebellar Control of Pain.

In the general population, transcranial anodal direct current stimulation of the cerebellum (ctDCS) reduces pain intensity and the amplitude of nociceptive laser evoked potentials (LEPs), whereas cathodal ctDCS elicits opposite effects. Since behavioral findings suggest that the cerebellar activity of highly hypnotizable individuals (highs) differs from the general population, we investigated whether hypnotizability-related differences occur in the modulation of pain by ctDCS. Sixteen healthy highs (according to the Stanford Hypnotic Susceptibility Scale, form A) and 16 participants not selected according to hypnotizability (controls) volunteered to undergo laser nociceptive stimulation of the dorsum of the left hand before and after anodal or cathodal ctDCS. LEPs amplitudes and latencies and the subjective pain experience (Numerical Rating Scale) were analyzed. Smaller LEP amplitudes and longer latencies were observed in highs with respect to controls independently of stimulation. After anodal and cathodal cerebellar stimulation, controls reported lower and higher pain than before it, respectively. In contrast, highs did not report significant changes in the perceived pain after both stimulations. They increased significantly their N2/P2 amplitude after anodal ctDCS and did not exhibit any significant change after cathodal tDCS, whereas controls decreased the N1 and N2P2 amplitude and increased their latency after anodal cerebellar stimulation and did the opposite after cathodal ctDCS. In conclusion, the study showed impaired cerebellar pain modulation and suggested altered cerebral cortical representation of pain in subjects with high hypnotizability scores.