Effects of GABA uptake inhibitors on posthypoxic myoclonus in rats

Lance-Adams Syndrome in the Intensive Care Unit: A Case Report

Lance-Adams syndrome (LAS), or chronic post-hypoxic myoclonus, is a myoclonic disorder following acute cerebral hypoxia after successful cardiopulmonary resuscitation (CPR). LAS is distinct from acute post-hypoxic myoclonus (acute PHM), presenting with myoclonic jerks and cerebellar ataxia after regaining consciousness. However, the overlap at the onset complicates differentiation and may lead to the withdrawal of life-sustaining measures, especially in sedated ICU patients. The presented case involves a 77-year-old male diagnosed with LAS post-CPR. Despite the presence of early myoclonic jerks EEG, laboratory testing, and neuroimaging showed no definitive proof of irreversible neurological damage. Once diagnosed, treatment involved sequential antiseizure medications and physical therapy when the patient achieved full consciousness. However, the patient ultimately faced severe disabilities and was unable to recover. This case report emphasizes the importance of limiting sedation, comprehensive clinical examination, and the use of complementary tests when no definitive proof of irreversible neurological damage is present after acute cerebral hypoxia. While LAS has a better vital prognosis than acute PHM, it is associated with poor neurofunctional recovery and chronic disability in most cases. Further research is essential for evidence-based management.

Brain regions and genes affecting myoclonus in animals

Myoclonus is defined as large-amplitude rhythmic movements. Brain regions underlying myoclonic jerks include brainstem, cerebellum, and cortex. Gamma-aminobutyric acid (GABA) appears to be the main neurotransmitter involved in myoclonus, possibly interacting with biogenic amines, opiates, acetylcholine, and glycine. Myoclonic jumping is a specific subtype seen in rodents, comprising rearing and hopping continuously against a wall. Myoclonic jumping can be seen in normal mouse strains, possibly as a result of simply being put inside a cage. Like other types, it is also triggered by changes in GABA, 5HT, and dopamine neurotransmission. Implicated brain regions include hippocampus and dorsal striatum, possibly with respect to D(1) dopamine, NMDA, and δ opioid receptors. There is reason to suspect that myoclonic jumping is underreported due to insufficient observations into mouse cages.

Lance-Adams syndrome: a report of two cases

Chronic post-hypoxic myoclonus, also known as Lance-Adams syndrome (LAS), is a rare complication of successful cardiopulmanry resuscitation often accompanied by action myoclonus and cerebellar ataxia. It is seen in patients who have undergone a cardiorespiratory arrest, regained consciousness afterwards, and then developed myoclonus days or weeks after the event. Worldwide, 122 cases have been reported in the literature so far, including 1 case of Chinese. Here we report 2 Chinese LAS patients with detailed neuroimagings. Cranial single photon emission computed tomography (SPECT) of patient 1, a 52-year-old woman, showed a mild hypoperfusion in her left temporal lobe, whereas patient 2, a 54-year-old woman, manifested a mild bilateral decrease of glucose metabolism in the frontal lobes and a mild to moderate decrease of the N-acetyl aspartate (NAA) peak in the bilateral hippocampi by cranial [(18)F]-fluorodeoxyglucose positron emission tomographic (PET) scan and cranial magnetic resonance spectroscopy (MRS), respectively. We also review the literature on the neuroimaging, pathogenesis, and treatment of LAS.

Effects of glutamate receptor antagonists on posthypoxic myoclonus in rats

Male Sprague-Dawley rats developed posthypoxic myoclonus following 10-min cardiac arrest and resuscitation. In current studies, roles of N-methyl-D-aspartate (NMDA), non-NMDA (a-amino-3-hydroxy-5-methylisoxazole-4-propionate, AMPA, and kainate), and metabotropic glutamate receptors in the pathophysiology of posthypoxic myoclonus were investigated. Treatments with the competitive or noncompetitive NMDA receptor antagonist, D(-)-2-amino-5-phosphonopentanoic acid (D[-]-AP-5) (ED50: 12.5 mg/kg, i.p.) or MK-801 maleate (ED50: 0.034 mg/kg, i.p.), and competitive or noncompetitive non-NMDA (AMPA/kainate) receptor antagonist, 6,7-dinitroquinoxaline-2,3-dione (DNQX) (ED50: 9.25 nM/5 microliters, i.c.v.) or 1-(4-ami -nophenyl)-4-methyl-7,8-methylenedioxy -5H-2,3-benzodiazepine hydrochloride (GYKI 52466) (ED50: 0.67 mg/kg, IP), significantly decreased myoclonus episodes in rats. On the other hand, treatment with the metabotropic glutamate receptor antagonist, L(+)-2-amino-3-phosphonopropionic acid (L[+]-AP-3) (50 or 500 nM/5 microliters, i.c.v., exerted no significant effect on myoclonus scores in posthypoxic rats. These results indicate that activation of NMDA and non-NMDA receptors receptors may mediate posthypoxic myoclonus in rats, whereas, involvement of metabotropic glutamate receptors needs to be studied further.