PubMed Health⌕ Search

Biomedical subjects

A J Sumner

Publications and source records attributed to A J Sumner.

At least 19 recordsLinked to original sources
PubMed2000

Unusual electrophysiological findings in X-linked dominant Charcot-Marie-Tooth disease.

X-linked Charcot-Marie-Tooth disease (CMTX) is the second most common form of Charcot-Marie-Tooth disease. Variable histopathological and nerve conduction velocity (NCV) results have suggested either a primary demyelinating or axonal polyneuropathy. We identified five individuals across three generations in a family with CMTX associated with a mutation in the gene coding for connexin 32. All individuals were studied by clinical neurological examination, DNA analysis, and nerve conduction studies. The proband (1174/KD) also underwent a sural nerve biopsy. As expected, all the affected males were more clinically affected than the females. All affected males and obligate female carriers exhibited some electrophysiological characteristics of demyelination. However, striking heterogeneity of nerve conduction velocities was seen. This family shows that CMTX is a heterogeneous and distinctly nonuniform demyelinating polyneuropathy, the severity of which varies with sex and age. Such electrophysiological variability is unique among hereditary neuropathies.

Charcot-Marie-Tooth Disease↗
PubMed2000

Electrophysiological features of inherited demyelinating neuropathies: A reappraisal in the era of molecular diagnosis.

The observation that inherited demyelinating neuropathies have uniform conduction slowing and that acquired disorders have nonuniform or multifocal slowing was made prior to the identification of mutations in myelin-specific genes which cause many of the inherited disorders involving peripheral nerve myelin. It is now clear that the electrophysiological aspects of these disorders are more complex than previously realized. Specifically, certain mutations appear to induce nonuniform slowing of conduction which resemble the findings in acquired demyelinating neuropathies. It is clinically important to recognize the different electrodiagnostic patterns of the various inherited demyelinating neuropathies. In addition, an understanding of the relationship between mutations of specific genes and their associated neurophysiological findings is likely to facilitate understanding of the role of these myelin proteins in peripheral nerve function and of how abnormalities in myelin proteins lead to neuropathy. We therefore review the current information on the electrophysiological features of the inherited demyelinating neuropathies in hopes of clarifying their electrodiagnostic features and to shed light on the physiological consequences of the different genetic mutations.

Electrophysiology↗
PubMed1999

Electrophysiologic features of inherited demyelinating neuropathies: a reappraisal.

The observation that inherited demyelinating neuropathies tend to have uniform conduction slowing and acquired disorders (CIDP and variants) have nonuniform or multifocal slowing was made before the identification of genetic defects of specific myelin constituents that cause the different forms of Charcot-Marie-Tooth and other inherited disorders involving peripheral nerve myelin. It is becoming clear that the electrophysiologic aspects of these disorders are more complex than previously realized. We review the current information available on the electrophysiologic features of the inherited demyelinating neuropathies in hopes of clarifying the clinical electrodiagnostic features of these disorders as well as to shed light on the physiologic consequences of the different genetic mutations.

Charcot-Marie-Tooth Disease↗
PubMed1998

Focal conduction block in n-hexane polyneuropathy.

A 19-year-old man with an asymptomatic history of recreational gasoline vapor inhalation presented with subacute progressive quadriparesis. For 2 weeks, he had intensely inhaled Coleman fuel oil vapor, which contains n-hexane. Nerve conduction studies including near-nerve needle stimulation showed focal conduction block in the bilateral median and ulnar nerves. Sural nerve biopsy was consistent with giant axonal neuropathy. Conduction block as seen in this case has not heretofore been described in n-hexane polyneuropathy.

Administration, Inhalation↗
PubMed1994

Postsurgical idiopathic brachial neuritis.

Idiopathic brachial neuritis (IBN) is a well-recognized clinical syndrome characterized by brachial pain followed by a patchy amyotrophy of muscles in the shoulder girdle and arm innervated by individual branches of the brachial plexus. Postsurgical IBN has not been widely recognized since Parsonage and Turner's original description in which 10% of patients had antecedent surgery. We present 6 patients who 1-13 days postoperatively developed signs and symptoms which met the clinical and electrophysiologic criteria for IBN. Postsurgical neuralgic amyotrophy is an under-recognized clinical entity which in most cases is ascribed to brachial plexus stretch injuries occurring during anesthesia. Early recognition of this condition may prevent unnecessary surgical exploration and allow for a more accurate prediction of functional recovery.

Adult↗
PubMed1994

Aberrant reinnervation following hypoglossal nerve damage.

Hypoglossal nerve damage is a known complication of carotid endarterectomy, occurring in approximately 5% of endarterectomies. The vast majority of these patients recover without functional disability from this injury even if the tongue remains hemiplegic. We report 2 patients who suffered hypoglossal nerve section during neck surgery. Although they were initially mildly symptomatic, they developed increasingly severe dysarthria and dysphagia beginning 4 months after surgery. EMG revealed abnormal coactivation of the genioglossus and styloglossus muscles on the affected side, suggesting aberrant reinnervation. Aberrant reinnervation is a well-known complication of facial nerve injury, but has not been previously recognized in hypoglossal nerve injury. Like the face, the tongue is composed of many muscles that must perform complex movements. Normally, injury to one hypoglossal nerve causes little or no disability, but when aberrant reinnervation occurs, the tongue no longer moves in a coordinated manner, and significant dysarthria ensues.

Aged↗
PubMed1994

Distal accentuation of conduction slowing in polyneuropathy associated with antibodies to myelin-associated glycoprotein and sulphated glucuronyl paragloboside.

In four patients with a chronic, demyelinating polyneuropathy associated with monoclonal IgM antibodies to myelin-associated glycoprotein (MAG) and sulphated glucuronyl paragloboside (SGPG), we have observed a marked prolongation of distal motor latencies disproportionate to proximal segment-conduction velocities, in nearly all nerves studied. Distal accentuation of conduction slowing distinguished these patients from those with Charcot-Marie-Tooth polyneuropathy type 1A, chronic inflammatory polyneuropathy, and from controls, as demonstrated by regression of distal motor latency on proximal conduction velocity. Sixteen of 21 nerves (76%) studied in the patients with anti-MAG/SGPG polyneuropathy had a terminal latency index of < or = 0.25 versus 11 of 195 nerves (6%) of Charcot-Marie-Tooth polyneuropathy type 1A patients, three of 49 nerves (6%) of patients with chronic inflammatory polyneuropathy and none of the controls (P = 0.0001). Recognition of this unique pattern of generalized, distally predominant conduction slowing in anti-MAG/SGPG polyneuropathy may be useful in clinically distinguishing this from other chronic demyelinating polyneuropathies, and in possibly providing insights into the pathophysiology of this disorder.

Aged↗
PubMed1992

Multifocal motor neuropathy.

We believe that our present understanding of these syndromes is insufficient to separate CIDP from MMN clearly and consider MMN to be a remarkably multifocal, predominantly motor variant of CIDP with the very unusual electrophysiologic feature of conduction block confined to motor axons. Further studies are clearly needed to clarify fully the relationship between CIDP and MMN and the relationship of MMN and other motor syndromes to various ganglioside antibodies.

Autoimmune Diseases↗
PubMed1990

A computer simulation of conduction block: effects produced by actual block versus interphase cancellation.

A reduction in compound muscle action potential (CMAP) amplitude and area following proximal versus distal stimulation is the accepted clinical hallmark of conduction block; however, quantitative criteria for determining conduction block remain ambiguous. In this study, digitized records of individual motor unit action potentials (MUAPs) elicited by incremental stimulation in vivo were arithmetically combined in a computer simulation of CMAP generation. Through simulation of possible phase interaction patterns of individual MUAPs, we have shown that abnormal temporal dispersion alone can produce reductions in CMAP area of up to 50%, values that are commonly thought to represent conduction block. Furthermore, by simulating conduction block without excessive temporal dispersion in defined subpopulations of axons, we have demonstrated the importance of the fastest conducting (largest MUAP) axons in determining CMAP amplitude and area. In conclusion, measurements of CMAP amplitude and area in determining conduction block may be misleading if there is significant abnormal temporal dispersion, and quantitation of the degree of conduction block is difficult without knowledge of which subpopulations of axons are affected.

Action Potentials↗