Nimeshan Geevasinga

Sensitivity and specificity of threshold tracking transcranial magnetic stimulation for diagnosis of amyotrophic lateral sclerosis: a prospective study

BACKGROUND Diagnosis of amyotrophic lateral sclerosis (ALS) remains problematic, with substantial diagnostic delays. We assessed the sensitivity and specificity of a threshold tracking transcranial magnetic stimulation (TMS) technique, which might allow early detection of upper motor neuron dysfunction, for the diagnosis of the disorder. METHODS We did a prospective study of patients referred to three neuromuscular centres in Sydney, Australia, in accordance with the Standards for Reporting of Diagnostic Accuracy. Participants had definite, probable, or possible ALS, as defined by the Awaji criteria; or pure motor disorder with clinical features of upper and lower motor neuron dysfunction in at least one body region, progressing over a 6 month follow-up period; or muscle wasting and weakness for at least 6 months. All patients underwent threshold tracking TMS at recruitment (index test), with application of the reference standard, the Awaji criteria, to differentiate patients with ALS from those with non-ALS disorders. The investigators who did the index test were masked to the results of the reference test and all other investigations. The primary outcome measures were the sensitivity and specificity of TMS in differentiating ALS from non-ALS disorders; these measures were derived from receiver operator curve analysis. FINDINGS Between Jan 1, 2010, and March 1, 2014, we screened 333 patients; 281 met our inclusion criteria. We eventually diagnosed 209 patients with ALS and 68 with non-ALS disorders; the diagnosis of four patients was inconclusive. The threshold tracking TMS technique differentiated ALS from non-ALS disorders with a sensitivity of 73·21% (95% CI 66·66-79·08) and specificity of 80·88% (69·53-89·40) at an early stage in the disease. All patients tolerated the study well, and we did not record any adverse events from performance of the index test. INTERPRETATION The threshold tracking TMS technique reliably distinguishes ALS from non-ALS disorders and, if these findings are replicated in larger studies, could represent a useful diagnostic investigation when combined with the Awaji criteria to prove upper motor neuron dysfunction at early stages of ALS. FUNDING Motor Neuron Disease Research Institute of Australia, National Health and Medical Research Council of Australia, and Pfizer.

Rabeprazole‐induced acute interstitial nephritis

SUMMARY:  Acute interstitial nephritis is an uncommon but important cause of acute renal failure. Proton pump inhibitors are now thought to be the most common class of drugs implicated in drug‐induced acute interstitial nephritis. This is the first reported case of rabeprazole‐induced acute interstitial nephritis.

Pathophysiological and diagnostic implications of cortical dysfunction in ALS

Cortical dysfunction — specifically, the development of hyperexcitability — seems to be an early and intrinsic feature of sporadic and familial amyotrophic lateral sclerosis (ALS) phenotypes, preceding the onset of lower motor neuron dysfunction and correlating with ensuing lower motor neuron dysfunction and degeneration. In fact, cortical dysfunction could provide a pathogenic basis for ALS, with corticomotor neuronal hyperexcitability mediating motor neuron degeneration via a trans-synaptic, glutamate-mediated, excitotoxic mechanism. The recent identification of C9orf72 repeat expansion as an important genetic risk factor for both ALS and frontotemporal dementia has underscored the importance of cortical function in ALS pathogenesis, and has helped to confirm that the disease forms part of a spectrum of central neurodegenerative processes. Changes in cortical function that develop in ALS could prove useful as diagnostic biomarkers, potentially enhancing the diagnosis of ALS at an early stage of the disease process. Pathophysiological and diagnostic biomarkers of cortical function might also provide insights to guide the development of future therapeutic approaches, including stem cell and genetic interventions, thereby providing potential for more-effective management of patients with ALS.

Cortical Function in Asymptomatic Carriers and Patients With C9orf72 Amyotrophic Lateral Sclerosis

IMPORTANCE 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). OBJECTIVE To investigate whether cortical hyperexcitability forms the pathophysiological basis of c9orf72 FALS using the threshold-tracking transcranial magnetic stimulation technique. DESIGN, SETTING, AND PARTICIPANTS 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. Results were compared with 73 patients with sporadic ALS and 74 healthy control participants. MAIN OUTCOMES AND MEASURES Cortical excitability variables, including short-interval intracortical inhibition, were measured in patients with c9orf72 FALS and results were compared with asymptomatic c9orf72 carriers, patients with sporadic ALS, and healthy control participants. RESULTS Mean (SD) short-interval intracortical inhibition was significantly reduced in patients with c9orf72 FALS (1.2% [1.8%]) and sporadic ALS (1.6% [1.2%]) compared with asymptomatic c9orf72 expansion carriers (10.2% [1.8%]; F = 16.1; P < .001) and healthy control participants (11.8% [1.0%]; F = 16.1; P < .001). The reduction of short-interval intracortical inhibition was accompanied by an increase in intracortical facilitation (P < .01) and motor-evoked potential amplitude (P < .05) as well as a reduction in the resting motor threshold (P < .05) and cortical silent period duration (P < .001). CONCLUSIONS AND RELEVANCE This study establishes cortical hyperexcitability as an intrinsic feature of symptomatic c9orf72 expansion-related ALS but not asymptomatic expansion carriers.

A retrospective review of X-linked Charcot-Marie-Tooth disease in childhood

Objective: X-linked Charcot-Marie-Tooth disease (CMTX) is infrequently diagnosed in childhood, and its clinical and neurophysiologic features are not well-described. We reviewed clinical, neurophysiologic, and pathologic findings in 17 children with CMTX. Methods: This was a retrospective review of children with CMTX from 2 tertiary pediatric hospitals. The diagnosis of CMTX was based on an identifiable connexin 32 mutation (CMTX1) or a consistent pedigree and neurophysiologic features in children without a connexin 32 mutation (CMTX-other). Results: Six boys and 2 girls from 8 kindreds had CMTX1, and 8 boys and 1 girl from 5 kindreds had other forms of CMTX (CMTX-other). Fifteen children, including males and carrier females, were symptomatic from infancy or early childhood (younger than 5 years). In addition to the typical Charcot-Marie-Tooth disease clinical phenotype, some patients had delayed motor development, sensorineural hearing loss, tremor, pathologic fractures, or transient CNS disturbances. Eleven children underwent nerve conduction studies. Median nerve motor nerve conduction velocities were in the intermediate to normal range (30–54 m/s) in all children older than 2 years. Axon loss, reflected by low-amplitude compound muscle action potentials, was present in all patients. A pattern of X-linked dominant inheritance, with carrier females showing an abnormal neurologic or neurophysiologic examination, correlated with the presence of a connexin 32 mutation in all but 2 pedigrees. Conclusions: The clinical phenotype of CMTX is broader than previously reported. Onset in males and carrier females is most often in early childhood. Families with an X-linked dominant inheritance pattern are likely to have CMTX1.

Diagnostic utility of cortical excitability studies in amyotrophic lateral sclerosis.

The diagnosis of amyotrophic lateral sclerosis (ALS) relies on identification of a combination of upper and lower motor neuron signs. In order to improve the diagnostic sensitivity for ALS, Awaji criteria were developed, in part to better incorporate neurophysiological measures, although assessment of upper motor neuron dysfunction remained clinically based. Given that cortical hyperexcitability appears to be an early feature in ALS, the present study assessed the diagnostic utility of a threshold tracking transcranial magnetic stimulation technique as an aid to the research‐based Awaji criteria in establishing an earlier diagnosis of ALS.

Cortical excitability changes distinguish the motor neuron disease phenotypes from hereditary spastic paraplegia

Cortical hyperexcitability has been identified as an important pathogenic mechanism in motor neuron disease (MND). The issue as to whether cortical hyperexcitability is a common process across the MND phenotypes, including amyotrophic lateral sclerosis (ALS) and primary lateral sclerosis (PLS), remains unresolved. Separately, the clinical distinction between PLS and ‘mimic disorders’ such as hereditary spastic paraparesis (HSP) may be difficult, potentially delaying diagnosis. Consequently, the aim of the present study was to determine the nature and spectrum of cortical excitability changes across the MND phenotypes, and to determine whether the presence of cortical dysfunction distinguishes PLS from HSP.

Diagnostic criteria in amyotrophic lateral sclerosis A multicenter prospective study

Objective: To assess the sensitivity and specificity of the Awaji and revised El Escorial diagnostic criteria (rEEC) in amyotrophic lateral sclerosis (ALS). Methods: We conducted a large prospective multicenter study, recruiting 416 patients (253 male, 163 female) between January 1, 2012, and August 31, 2015, to compare the diagnostic accuracy of Awaji and rEEC in accordance with standards of reporting of diagnostic accuracy criteria. Results: The sensitivity of the Awaji criteria (57%, 50.0%–63.3%) was higher when compared to rEEC (45%, 38.7%–51.7%, p < 0.001), translating to a 12% gain in sensitivity. The specificity of the both criteria were identical, 99.5%, indicating the number needed to test in order to diagnose one extra case of ALS was 1.8 (1.5–2) for Awaji criteria and 2.4 (2–2.6) for rEEC. The Awaji criteria exhibited a higher sensitivity across subgroups, including bulbar (p < 0.001) and limb-onset (p < 0.001) patients. The inclusion of the possible diagnostic category as a positive finding enhanced sensitivity of the Awaji criteria and rEEC, particularly in early stages of ALS, while maintaining specificity. Conclusion: The present study established a higher sensitivity of Awaji criteria when compared to rEEC, with diagnostic benefits evident in bulbar and limb-onset disease. Inclusion of possible as a positive finding enhanced sensitivity of both criteria, while maintaining specificity, and should be considered in clinical practice and future therapeutic trials. Classification of evidence: This study provides Class IV evidence that the Awaji criteria have a higher sensitivity and the same specificity as the rEEC in identifying patients with ALS.

Juvenile Huntington disease

Abstract:  Huntington disease (HD) is a dominantly inherited neurodegenerative disorder related to expansion of a triplet repeat sequence in the huntington gene on chromosome 4. Adult HD usually presents with chorea and personality changes. Juvenile HD is far less common and presents with parkinsonism, dystonia and seizures. We report a case of juvenile HD, showing extreme anticipation, in which diagnosis was delayed because of failure to recognise the significance of the family history and the characteristic clinical and radiologic features of this condition.

Axonal Ion Channel Dysfunction in C9orf72 Familial Amyotrophic Lateral Sclerosis

IMPORTANCE Abnormalities of axonal excitability characterized by upregulation of persistent sodium (Na+) conductances and reduced potassium (K+) currents have been reported in sporadic amyotrophic lateral sclerosis (SALS) phenotypes and linked to the development of clinical features such as fasciculations and neurodegeneration. OBJECTIVE To investigate whether abnormalities of axonal ion channel function, particularly upregulation of persistent Na+ conductances and reduced K+ currents, form the pathophysiological basis of chromosome 9 open reading frame 72 (c9orf72) familial amyotrophic lateral sclerosis (FALS). DESIGN, SETTING, AND PARTICIPANTS This was a prospective study. Clinical and functional assessment, along with motor-nerve excitability studies, were undertaken in 10 clinically affected patients with c9orf72 FALS, 9 asymptomatic c9orf72 mutation carriers, and 21 patients with SALS from 3 hospitals and 2 outpatient clinics. MAIN OUTCOMES AND MEASURES Axonal excitability variables were measured in patients with c9orf72 ALS and results compared with matched patients with SALS and healthy control participants. RESULTS Strength-duration time constant (τSD) was significantly increased in the patients with c9orf72 FALS and those with SALS (mean [SD], c9orf72 FALS: 0.50 [0.02] milliseconds; SALS: 0.52 [0.02] milliseconds; P < .01) when compared with control participants (mean [SD], 0.44 [0.01] milliseconds). In contrast, there were no significant changes of τSD in asymptomatic c9orf72 mutation carriers (P = .42). An accompanying increase in depolarizing threshold electrotonus at 90 to 100 milliseconds (TEd 90-100 milliseconds) was also evident in the c9orf72 FALS (P < .05) and SALS (P < .01) cohorts. Mathematical modeling suggested that an increase in persistent Na+ conductances, along with reduced K+ currents, best explained the changes in axonal excitability. Importantly, these abnormalities in axonal excitability correlated with the motor amplitude (τSD: R = -0.38, P < .05 and TEd 90-100 milliseconds: R = -0.44, P < .01), muscle weakness (TEd 90-100 milliseconds: R = -0.32, P < .05), and the ALS Functional Rating Scale (TEd 90-100 milliseconds: R = -0.34, P < .05). CONCLUSIONS AND RELEVANCE Findings from the present study establish that upregulation of persistent Na+ conductances and reduced K+ currents were evident in both c9orf72 FALS and SALS cohorts, and these changes in axonal excitability were associated with motor neuron degeneration.