A 16-year-old boy presented with rapidly progressive ascending paralysis 1 hour after eating raw ... more A 16-year-old boy presented with rapidly progressive ascending paralysis 1 hour after eating raw salmon. Seafood poisoning was initially considered. Although salmon is not a common cause of toxic seafood poisoning, cases have been reported in the Pacific region. The patient rapidly developed acute left heart and respiratory failure, and investigations revealed a rare tracking intramedullary haematoma of the spinal cord. Structural abnormalities of the central nervous system may present with acute paralysis and spinal shock, mimicking toxicological syndromes.
The identification of the chromosome 9 open reading frame 72 (c9orf72) gene hexanucleotide repeat... more The identification of the chromosome 9 open reading frame 72 (c9orf72) gene hexanucleotide repeat expansion represents a major advance in the understanding of amyotrophic lateral sclerosis (ALS) pathogenesis. The pathophysiological mechanism by which the c9orf72 gene expansion leads to neurodegeneration is not yet elucidated. Cortical hyperexcitability is potentially an important pathophysiological process in sporadic ALS and familial ALS (FALS). To investigate whether cortical hyperexcitability forms the pathophysiological basis of c9orf72 FALS using the threshold-tracking transcranial magnetic stimulation technique. Prospective case-control single-center study that took place at hospitals and outpatient clinics from January 1, 2013, to January 1, 2015. Clinical and functional assessments along with transcranial magnetic stimulation studies were taken on 15 patients with c9orf72 FALS and 11 asymptomatic expansion carriers of c9orf72 who were longitudinally followed up for 3 years. ...
A 16-year-old boy presented with rapidly progressive ascending paralysis 1 hour after eating raw ... more A 16-year-old boy presented with rapidly progressive ascending paralysis 1 hour after eating raw salmon. Seafood poisoning was initially considered. Although salmon is not a common cause of toxic seafood poisoning, cases have been reported in the Pacific region. The patient rapidly developed acute left heart and respiratory failure, and investigations revealed a rare tracking intramedullary haematoma of the spinal cord. Structural abnormalities of the central nervous system may present with acute paralysis and spinal shock, mimicking toxicological syndromes.
To investigate inter-rater and intra-rater reliability of electrical perceptual threshold (EPT) t... more To investigate inter-rater and intra-rater reliability of electrical perceptual threshold (EPT) testing in assessing somatosensory function in healthy volunteers. Prospective experimental. Hospital-based spinal cord injuries unit. Cutaneous electrical stimulation of 4 dermatomes at ASIA sensory key points (C3, T1, L3, and S2) was performed on 40 control subjects. The lowest ascending stimulus intensity at which sensation was perceived was recorded as the EPT. Mean EPT values for each dermatome, as determined by 2 testers at 2 time points, were examined and plotted against a normative template. Differences and associations between intra- and inter-rater measurements and left-right measurements were studied. EPT results for 2 people with spinal cord injuries were also examined. EPT measurements from left and right sides, obtained from the 2 time points and 2 testers, were found to be strongly associated, with the exception of left and right side measurements at the S2 dermatome. No si...
Critical illness polyneuropathy in burn patients is an underreported condition. It is associated ... more Critical illness polyneuropathy in burn patients is an underreported condition. It is associated with high mortality rates and prolonged hospital stay and rehabilitation. This study aims to further define the cause and outcome of critical illness polyneuropathy following major burn injuries. A retrospective review of all burn patients with neuropathy that presented to Royal North Shore Hospital, Sydney, between the period of 2004 and 2009 was performed. The neurological findings, diagnostic processes, and outcomes were examined. End points such as duration on the ventilator, length of intensive care, and hospital stay were recorded. There were 7 patients in total that exhibited abnormal neurological findings. Ages ranged from 17 to 43 years with all injuries sustained in flame burns. Mean total burnt surface area is 46%. There was no mortality in this series but all 7 had evidence of sepsis and multiorgan failure with an average 42 days spent on the ventilator. Clinical findings var...
Clinical record We report anoxic convulsions occurring in two medical students competing in a bre... more Clinical record We report anoxic convulsions occurring in two medical students competing in a breath-hold dive competition in shallow water. The seizure-like activity occurred during a competition called the “Dolphin Dive”, which was part of a university medical school swimming ...
Acquired and hereditary amyloidosis can cause peripheral neuropathy, but the mechanisms by which ... more Acquired and hereditary amyloidosis can cause peripheral neuropathy, but the mechanisms by which this occurs have not been established. Threshold tracking techniques allow in vivo assessment of the properties of the axonal membrane and may shed light on pathogenetic mechanisms underlying neuropathic disorders. We studied 10 subjects with primary amyloidosis using conventional nerve conduction studies and quantitative sensory, autonomic, and axonal excitability testing of median motor and sensory fibers. As expected, subjects with amyloidosis had evidence of small- and large-fiber neuropathy on conventional testing. There was no significant difference in axonal excitability between subjects and controls apart from the stimulus required to activate sensory fibers. Amyloid-related neuropathy does not produce a change in membrane potential as either a primary or secondary event. This suggests that ischemia and axonal compression are unlikely mechanisms for the neuropathy. Muscle Nerve 51: 443-445, 2015.
Poliomyelitis causes selective destruction of anterior horn cells and usually has a stable diseas... more Poliomyelitis causes selective destruction of anterior horn cells and usually has a stable disease course post-infection. We assessed the excitability characteristics in patients with a stable course after past poliomyelitis and compared them with changes described in amyotrophic lateral sclerosis (ALS). The excitability characteristics of motor and sensory nerves were studied in 10 subjects with stable past poliomyelitis. Motor rheobase was increased, but there were no significant changes in strength-duration properties or depolarizing threshold electrotonus, as have been seen in previous studies of ALS. There is minimal change in axonal excitability properties in patients with stable past poliomyelitis. The results may signify sufficient compensation in the stable state of the disease. Increased subexcitability in 1 subject with demonstrable hyperexcitability may represent compensation for increased ectopic activity rather than a different process in surviving motor neurons. Muscle Nerve 50: 602-604, 2014.
In mitochondrial disease, it is likely that energy substrate depletion leads to paralysis of ATPa... more In mitochondrial disease, it is likely that energy substrate depletion leads to paralysis of ATPase-dependent pumps, resulting in membrane depolarization. Axonal depolarization has been demonstrated in a crisis, but not in the resting state. We, therefore, stressed axons using ischemia to see if this would reveal abnormal responses, as occurs in diabetes mellitus. Excitability of median nerve axons at the wrist was studied in 13 patients with MELAS (6 with glucose intolerance) and 17 control subjects in response to ischemia due to inflation of a cuff around the arm for 10 min. There were no significant differences in preischemic measures of axonal excitability or in the intra- and postischemic responses. Although depolarization has been noted to occur spontaneously during a crisis, we could not demonstrate a defect of axonal ATP-dependent mechanisms. The mechanisms underlying axonal excitability and neuropathy in diabetes may not apply to MELAS.
A 16-year-old boy presented with rapidly progressive ascending paralysis 1 hour after eating raw ... more A 16-year-old boy presented with rapidly progressive ascending paralysis 1 hour after eating raw salmon. Seafood poisoning was initially considered. Although salmon is not a common cause of toxic seafood poisoning, cases have been reported in the Pacific region. The patient rapidly developed acute left heart and respiratory failure, and investigations revealed a rare tracking intramedullary haematoma of the spinal cord. Structural abnormalities of the central nervous system may present with acute paralysis and spinal shock, mimicking toxicological syndromes.
The identification of the chromosome 9 open reading frame 72 (c9orf72) gene hexanucleotide repeat... more The identification of the chromosome 9 open reading frame 72 (c9orf72) gene hexanucleotide repeat expansion represents a major advance in the understanding of amyotrophic lateral sclerosis (ALS) pathogenesis. The pathophysiological mechanism by which the c9orf72 gene expansion leads to neurodegeneration is not yet elucidated. Cortical hyperexcitability is potentially an important pathophysiological process in sporadic ALS and familial ALS (FALS). To investigate whether cortical hyperexcitability forms the pathophysiological basis of c9orf72 FALS using the threshold-tracking transcranial magnetic stimulation technique. Prospective case-control single-center study that took place at hospitals and outpatient clinics from January 1, 2013, to January 1, 2015. Clinical and functional assessments along with transcranial magnetic stimulation studies were taken on 15 patients with c9orf72 FALS and 11 asymptomatic expansion carriers of c9orf72 who were longitudinally followed up for 3 years. ...
A 16-year-old boy presented with rapidly progressive ascending paralysis 1 hour after eating raw ... more A 16-year-old boy presented with rapidly progressive ascending paralysis 1 hour after eating raw salmon. Seafood poisoning was initially considered. Although salmon is not a common cause of toxic seafood poisoning, cases have been reported in the Pacific region. The patient rapidly developed acute left heart and respiratory failure, and investigations revealed a rare tracking intramedullary haematoma of the spinal cord. Structural abnormalities of the central nervous system may present with acute paralysis and spinal shock, mimicking toxicological syndromes.
To investigate inter-rater and intra-rater reliability of electrical perceptual threshold (EPT) t... more To investigate inter-rater and intra-rater reliability of electrical perceptual threshold (EPT) testing in assessing somatosensory function in healthy volunteers. Prospective experimental. Hospital-based spinal cord injuries unit. Cutaneous electrical stimulation of 4 dermatomes at ASIA sensory key points (C3, T1, L3, and S2) was performed on 40 control subjects. The lowest ascending stimulus intensity at which sensation was perceived was recorded as the EPT. Mean EPT values for each dermatome, as determined by 2 testers at 2 time points, were examined and plotted against a normative template. Differences and associations between intra- and inter-rater measurements and left-right measurements were studied. EPT results for 2 people with spinal cord injuries were also examined. EPT measurements from left and right sides, obtained from the 2 time points and 2 testers, were found to be strongly associated, with the exception of left and right side measurements at the S2 dermatome. No si...
Critical illness polyneuropathy in burn patients is an underreported condition. It is associated ... more Critical illness polyneuropathy in burn patients is an underreported condition. It is associated with high mortality rates and prolonged hospital stay and rehabilitation. This study aims to further define the cause and outcome of critical illness polyneuropathy following major burn injuries. A retrospective review of all burn patients with neuropathy that presented to Royal North Shore Hospital, Sydney, between the period of 2004 and 2009 was performed. The neurological findings, diagnostic processes, and outcomes were examined. End points such as duration on the ventilator, length of intensive care, and hospital stay were recorded. There were 7 patients in total that exhibited abnormal neurological findings. Ages ranged from 17 to 43 years with all injuries sustained in flame burns. Mean total burnt surface area is 46%. There was no mortality in this series but all 7 had evidence of sepsis and multiorgan failure with an average 42 days spent on the ventilator. Clinical findings var...
Clinical record We report anoxic convulsions occurring in two medical students competing in a bre... more Clinical record We report anoxic convulsions occurring in two medical students competing in a breath-hold dive competition in shallow water. The seizure-like activity occurred during a competition called the “Dolphin Dive”, which was part of a university medical school swimming ...
Acquired and hereditary amyloidosis can cause peripheral neuropathy, but the mechanisms by which ... more Acquired and hereditary amyloidosis can cause peripheral neuropathy, but the mechanisms by which this occurs have not been established. Threshold tracking techniques allow in vivo assessment of the properties of the axonal membrane and may shed light on pathogenetic mechanisms underlying neuropathic disorders. We studied 10 subjects with primary amyloidosis using conventional nerve conduction studies and quantitative sensory, autonomic, and axonal excitability testing of median motor and sensory fibers. As expected, subjects with amyloidosis had evidence of small- and large-fiber neuropathy on conventional testing. There was no significant difference in axonal excitability between subjects and controls apart from the stimulus required to activate sensory fibers. Amyloid-related neuropathy does not produce a change in membrane potential as either a primary or secondary event. This suggests that ischemia and axonal compression are unlikely mechanisms for the neuropathy. Muscle Nerve 51: 443-445, 2015.
Poliomyelitis causes selective destruction of anterior horn cells and usually has a stable diseas... more Poliomyelitis causes selective destruction of anterior horn cells and usually has a stable disease course post-infection. We assessed the excitability characteristics in patients with a stable course after past poliomyelitis and compared them with changes described in amyotrophic lateral sclerosis (ALS). The excitability characteristics of motor and sensory nerves were studied in 10 subjects with stable past poliomyelitis. Motor rheobase was increased, but there were no significant changes in strength-duration properties or depolarizing threshold electrotonus, as have been seen in previous studies of ALS. There is minimal change in axonal excitability properties in patients with stable past poliomyelitis. The results may signify sufficient compensation in the stable state of the disease. Increased subexcitability in 1 subject with demonstrable hyperexcitability may represent compensation for increased ectopic activity rather than a different process in surviving motor neurons. Muscle Nerve 50: 602-604, 2014.
In mitochondrial disease, it is likely that energy substrate depletion leads to paralysis of ATPa... more In mitochondrial disease, it is likely that energy substrate depletion leads to paralysis of ATPase-dependent pumps, resulting in membrane depolarization. Axonal depolarization has been demonstrated in a crisis, but not in the resting state. We, therefore, stressed axons using ischemia to see if this would reveal abnormal responses, as occurs in diabetes mellitus. Excitability of median nerve axons at the wrist was studied in 13 patients with MELAS (6 with glucose intolerance) and 17 control subjects in response to ischemia due to inflation of a cuff around the arm for 10 min. There were no significant differences in preischemic measures of axonal excitability or in the intra- and postischemic responses. Although depolarization has been noted to occur spontaneously during a crisis, we could not demonstrate a defect of axonal ATP-dependent mechanisms. The mechanisms underlying axonal excitability and neuropathy in diabetes may not apply to MELAS.
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