Gregory T. Carter

Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a severe, progressive, X-linked muscle-wasting disorder with an incidence of -1/3,500 male births. Females are also affected, in rare instances. The manifestation of mild to severe symptoms in female carriers of dystrophin mutations is often the result of the preferential inactivation of the X chromosome carrying the normal dystrophin gene. The severity of the symptoms is dependent on the proportion of cells that have inactivated the normal X chromosome. A skewed pattern ofX inactivation is also responsible for the clinical manifestation of DMD in females carrying X; autosome translocations, which disrupt the dystrophin gene. DMD may also be observed in females with Turner syndrome (45,X), if the remaining X chromosome carries a DMD mutation. We report here the case of a karyotypically normal female affected with DMD as a result of homozygosity for a deletion of exon 50 of the dystrophin gene. PCR analysis of microsatellite markers spanning the length of the X chromosome demonstrated that homozygosity for the dystrophin gene mutation was caused by maternal isodisomy for the entire X chromosome. This finding demonstrates that uniparental isodisomy of the X chromosome is an additional mechanism for the expression of Xlinked recessive disorders. The probands clinical presentation is consistent with the absence of imprinted genes (i.e., genes that are selectively expressed based on the parent of origin) on the X chromosome.Fifteen subjects with Beckers muscular dystrophy (BMD) were studied prospectively over a 10-yr period to provide a profile of impairment and disability. Proximal lower extremity musculature (particularly the hip and knee extensors), ankle dorsiflexors, and neck flexors showed significantly early weakness. Extensor muscle groups were weaker than flexor muscles at the elbow and knee. The mean manual muscle test (MMT) strength grade for all muscle groups combined was 3.7 +/- 0.8 MMT units. There was a slowly progressive decline in strength, only -0.31 MMT units per decade, and the decline was relatively equal in all muscle groups. There was not side dominance. Severe contractures did not appear to be a problem until after transition to a wheelchair, and scoliosis was rare. Restrictive lung disease occurred as a late complication in a small percentage of cases; however, maximal expiratory pressure was significantly reduced early in the disease. Only two individuals (19%) had severe restrictive lung disease and a history of significant respiratory complications. There was a slight but significant decline in forced vital capacity and maximal expiratory pressure with age and disease duration. The cardiomyopathy in BMD appeared to be disproportionately severe in some cases. Eleven individuals (73%) had abnormal electrocardiograms, and five (25%) had a history of significant cardiovascular complication, with no age or disease duration effect. Functional evaluations and timed motor performance tests showed only mild disability in most individuals. Mean intellectual and neuropsychologic function was within normal limits, but with a large variability in intelligence quotient scores. This report and others suggest a tremendous heterogeneity of severity among males with BMD.

Distal symmetric polyneuropathy: A definition for clinical research: Report of the American Academy of Neurology, the American Association of Electrodiagnostic Medicine, and the American Academy of Physical Medicine and Rehabilitation

The objective of this report was to develop a case definition of distal symmetric polyneuropathy to standardize and facilitate clinical research and epidemiologic studies. A formalized consensus process was employed to reach agreement after a systematic review and classification of evidence from the literature. The literature indicates that symptoms alone have relatively poor diagnostic accuracy in predicting the presence of polyneuropathy; signs are better predictors of polyneuropathy than symptoms; and single abnormalities on examination are less sensitive than multiple abnormalities in predicting the presence of polyneuropathy. The combination of neuropathic symptoms, signs, and electrodiagnostic findings provides the most accurate diagnosis of distal symmetric polyneuropathy. A set of case definitions was rank ordered by likelihood of disease. The highest likelihood of polyneuropathy (useful for clinical trials) occurs with a combination of multiple symptoms, multiple signs, and abnormal electrodiagnostic studies. A modest likelihood of polyneuropathy (useful for field or epidemiologic studies) occurs with a combination of multiple symptoms and multiple signs when the results of electrodiagnostic studies are not available. A lower likelihood of polyneuropathy occurs when electrodiagnostic studies and signs are discordant. For research purposes, the best approach to defining distal symmetric polyneuropathy is a set of case definitions rank ordered by estimated likelihood of disease. The inclusion of this formalized case definition in clinical and epidemiologic research studies will ensure greater consistency of case selection.

Practice Parameter: Evaluation of distal symmetric polyneuropathy: Role of autonomic testing, nerve biopsy, and skin biopsy (an evidence-based review) Report of the American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and American Academy of Physical Medicine and Rehabilitation

Background: Distal symmetric polyneuropathy (DSP) is the most common variety of neuropathy. Since the evaluation of this disorder is not standardized, the available literature was reviewed to provide evidence-based guidelines regarding the role of autonomic testing, nerve biopsy, and skin biopsy for the assessment of polyneuropathy. Methods: A literature review using MEDLINE, EMBASE, and Current Contents was performed to identify the best evidence regarding the evaluation of polyneuropathy published between 1980 and March 2007. Articles were classified according to a four-tiered level of evidence scheme and recommendations were based upon the level of evidence. Results and Recommendations: 1) Autonomic testing should be considered in the evaluation of patients with polyneuropathy to document autonomic nervous system dysfunction (Level B). Such testing should be considered especially for the evaluation of suspected autonomic neuropathy (Level B) and distal small fiber sensory polyneuropathy (SFSN) (Level C). A battery of validated tests is recommended to achieve the highest diagnostic accuracy (Level B). 2) Nerve biopsy is generally accepted as useful in the evaluation of certain neuropathies as in patients with suspected amyloid neuropathy, mononeuropathy multiplex due to vasculitis, or with atypical forms of chronic inflammatory demyelinating polyneuropathy (CIDP). However, the literature is insufficient to provide a recommendation regarding when a nerve biopsy may be useful in the evaluation of DSP (Level U). 3) Skin biopsy is a validated technique for determining intraepidermal nerve fiber density and may be considered for the diagnosis of DSP, particularly SFSN (Level C). There is a need for additional prospective studies to define more exact guidelines for the evaluation of polyneuropathy. AAN = American Academy of Neurology; AANEM = American Academy of Neuromuscular and Electrodiagnostic Medicine; AAPM&R = American Academy of Physical Medicine and Rehabilitation; ART = autonomic reflex testing; BRSI = baroreflex sensitivity index; CASS = composite autonomic scoring scale; CIDP = chronic inflammatory demyelinating polyneuropathy; DSFN = distal small fiber neuropathy; DSP = distal symmetric polyneuropathy; EDx = electrodiagnosis; EFNS = European Federation of Neurological Societies; HRV = heart rate variability; IAN = idiopathic autonomic neuropathy; IENF = intraepidermal nerve fibers; MSNA = muscle sympathetic nerve activity; NCSs = nerve conduction studies; PGP 9.5 = protein-gene-product 9.5; PN = peripheral neuropathy; PRT = blood pressure recovery time; QAE = quantitative autonomic examination; QSART = quantitative sudomotor axon reflex test; QSS = Quality Standards Subcommittee; QST = quantitative sensory testing; SFSN = small fiber sensory polyneuropathy; TST = thermoregulatory sweat testing.

Practice parameter: the evaluation of distal symmetric polyneuropathy: the role of autonomic testing, nerve biopsy, and skin biopsy (an evidence-based review). Report of the American Academy of Neurology, the American Association of Neuromuscular and Electrodiagnostic Medicine, and the American Academy of Physical Medicine and Rehabilitation.

Distal symmetric polyneuropathy (DSP) is the most common variety of neuropathy. Since the evaluation of this disorder is not standardized, the available literature was reviewed to provide evidence‐based guidelines regarding the role of autonomic testing, nerve biopsy and skin biopsy for the assessment of polyneuropathy.

Practice Parameter: Evaluation of distal symmetric polyneuropathy: Role of laboratory and genetic testing (an evidence-based review) Report of the American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and American Academy of Physical Medicine and Rehabilitation

Background: Distal symmetric polyneuropathy (DSP) is the most common variety of neuropathy. Since the evaluation of this disorder is not standardized, the available literature was reviewed to provide evidence-based guidelines regarding the role of laboratory and genetic tests for the assessment of DSP. Methods: A literature review using MEDLINE, EMBASE, and Current Contents was performed to identify the best evidence regarding the evaluation of polyneuropathy published between 1980 and March 2007. Articles were classified according to a four-tiered level of evidence scheme and recommendations were based upon the level of evidence. Results and Recommendations: 1) Screening laboratory tests may be considered for all patients with polyneuropathy (Level C). Those tests that provide the highest yield of abnormality are blood glucose, serum B12 with metabolites (methylmalonic acid with or without homocysteine), and serum protein immunofixation electrophoresis (Level C). If there is no definite evidence of diabetes mellitus by routine testing of blood glucose, testing for impaired glucose tolerance may be considered in distal symmetric sensory polyneuropathy (Level C). 2) Genetic testing should be conducted for the accurate diagnosis and classification of hereditary neuropathies (Level A). Genetic testing may be considered in patients with cryptogenic polyneuropathy who exhibit a hereditary neuropathy phenotype (Level C). Initial genetic testing should be guided by the clinical phenotype, inheritance pattern, and electrodiagnostic features and should focus on the most common abnormalities which are CMT1A duplication/HNPP deletion, Cx32 (GJB1), and MFN2 mutation screening. There is insufficient evidence to determine the usefulness of routine genetic testing in patients with cryptogenic polyneuropathy who do not exhibit a hereditary neuropathy phenotype (Level U). AAN = American Academy of Neurology; AANEM = American Academy of Neuromuscular and Electrodiagnostic Medicine; AAPM&R = American Academy of Physical Medicine and Rehabilitation; CMT = Charcot-Marie-Tooth; DSP = distal symmetric polyneuropathy; EDX = electrodiagnostic; GTT = glucose tolerance testing; IFE = immunofixation electrophoresis; QSS = Quality Standards Subcommittee; SPEP = serum protein electrophoresis.

Clinical features of late-onset Pompe disease: a prospective cohort study.

The objective of this 12‐month study was to describe the clinical features of late‐onset Pompe disease and identify appropriate outcome measures for use in clinical trials. Assessments included quantitative muscle testing (QMT), functional activities (FAA), 6‐min walk test (6MWT), and pulmonary function testing (PFT). Percent predicted values indicated quantifiable upper and lower extremity weakness, impaired walking ability, and respiratory muscle weakness. Significant declines in arm and leg strength and pulmonary function were observed during the study period. The outcome measures were demonstrated to be safe and reliable. Symptom duration was identified as the best predictor of the extent of skeletal and respiratory muscle weakness. Muscle Nerve 38: 1236–1245, 2008

Assessment of pain and health-related quality of life in slowly progressive neuromuscular disease

Few studies have examined the effect of pain on the quality of life of individuals with slowly progressive neuromuscular disease (NMD). The purpose of this study was to determine the frequency and extent to which subjects with slowly progressive NMD report pain and the association between pain and health-related quality of life in persons with NMD. The study design was a descriptive, nonexperimental survey. Of a total of 1,432 subjects with slowly progressive NMDs recruited from a university-based NMD clinic and the membership rosters of worldwide NMD support organizations, 859 agreed to participate. The primary measurement tool used was the Medical Outcomes Study SF-36 health survey. Our results indicated that, with the exception of adult spinal muscular atrophy (SMA), the frequency and severity of pain reported in slowly progressive NMDs was significantly greater than levels of pain reported by the general US population and was comparable to pain reported by subjects with osteoarthritis and chronic low back pain. There was a significant correlation between increased pain and lower levels of general health, vitality, social function, and physical role. Pain was moderately associated with increased fatigue, inability to cope adequately with stress, and sleep disturbance. In conclusion, with the exception of adult SMA, the frequency and severity of pain reported in slowly progressive NMDs was significant.

Practice Parameter: The Evaluation of Distal Symmetric Polyneuropathy: The Role ofLaboratory and Genetic Testing (An Evidence-Based Review): Report of the American Academy of Neurology, the American Association of Neuromuscular and Electrodiagnostic Medicine, and the American Academy of Physical Medicine and Rehabilitation

Distal symmetric polyneuropathy (DSP) is the most common variety of neuropathy. Since the evaluation of this disorder is not standardized, the available literature was reviewed to provide evidence‐based guidelines regarding the role of laboratory and genetic tests for the assessment of DSP.

Neuropathic Pain in Charcot-Marie-Tooth Disease

OBJECTIVES To determine the frequency and extent to which subjects with Charcot-Marie-Tooth (CMT) disease report pain and to compare qualities of pain in CMT to other painful neuropathic conditions. STUDY DESIGN Descriptive, nonexperimental survey, using a previously validated measurement tool, the Neuropathic Pain Scale (NPS). PARTICIPANTS Participants were recruited from the membership roster of a worldwide CMT support organization. MAIN OUTCOME MEASURES NPS pain descriptors reported in CMT were compared with those reported by subjects with postherpetic neuralgia (PHN), complex regional pain syndrome, type 1 (CRPS-1), also known as reflex sympathetic dystrophy, diabetic neuropathy (DN), and peripheral nerve injury (PNI). RESULTS Of 617 CMT subjects (40% response rate), 440 (71%) reported pain. with the most severe pain sites noted as low back (70%), knees (53%), ankles (50%), toes (46%), and feet (44%). Of this group, 171 (39%) reported interruption of activities of daily living by pain; 168 (38%) used non-narcotic pain medication and 113 (23%) used narcotics and/or benzodiazepines for pain. The use of pain description was similar for CMT, PHN, CRPS-1, DN, and PNI in terms of intensity and the descriptors hot, dull, and deep. CONCLUSIONS Neuropathic pain is a significant problem for many people with CMT. The frequency and intensity of pain reported in CMT is comparable in many ways to PHN, CRPS-1, DN. and PNI. Further studies are needed to examine possible pain generators and pharmacologic and rehabilitative modalities to treat pain in CMT.

Evidence-based guideline summary: Diagnosis and treatment of limb-girdle and distal dystrophies Report of the Guideline Development Subcommittee of the American Academy of Neurology and the Practice Issues Review Panel of the American Association of Neuromuscular & Electrodiagnostic Medicine

OBJECTIVE To review the current evidence and make practice recommendations regarding the diagnosis and treatment of limb-girdle muscular dystrophies (LGMDs). METHODS Systematic review and practice recommendation development using the American Academy of Neurology guideline development process. RESULTS Most LGMDs are rare, with estimated prevalences ranging from 0.07 per 100,000 to 0.43 per 100,000. The frequency of some muscular dystrophies varies based on the ethnic background of the population studied. Some LGMD subtypes have distinguishing features, including pattern of muscle involvement, cardiac abnormalities, extramuscular involvement, and muscle biopsy findings. The few published therapeutic trials were not designed to establish clinical efficacy of any treatment. PRINCIPAL RECOMMENDATIONS For patients with suspected muscular dystrophy, clinicians should use a clinical approach to guide genetic diagnosis based on clinical phenotype, inheritance pattern, and associated manifestations (Level B). Clinicians should refer newly diagnosed patients with an LGMD subtype and high risk of cardiac complications for cardiology evaluation even if they are asymptomatic from a cardiac standpoint (Level B). In patients with LGMD with a known high risk of respiratory failure, clinicians should obtain periodic pulmonary function testing (Level B). Clinicians should refer patients with muscular dystrophy to a clinic that has access to multiple specialties designed specifically to care for patients with neuromuscular disorders (Level B). Clinicians should not offer patients with LGMD gene therapy, myoblast transplantation, neutralizing antibody to myostatin, or growth hormone outside of a research study designed to determine efficacy and safety of the treatment (Level R). Detailed results and recommendations are available on the Neurology® Web site at Neurology.org.Objective: To review the current evidence and make practice recommendations regarding the diagnosis and treatment of limb-girdle muscular dystrophies (LGMDs). Methods: Systematic review and practice recommendation development using the American Academy of Neurology guideline development process. Results: Most LGMDs are rare, with estimated prevalences ranging from 0.07 per 100,000 to 0.43 per 100,000. The frequency of some muscular dystrophies varies based on the ethnic background of the population studied. Some LGMD subtypes have distinguishing features, including pattern of muscle involvement, cardiac abnormalities, extramuscular involvement, and muscle biopsy findings. The few published therapeutic trials were not designed to establish clinical efficacy of any treatment. Principal recommendations: For patients with suspected muscular dystrophy, clinicians should use a clinical approach to guide genetic diagnosis based on clinical phenotype, inheritance pattern, and associated manifestations (Level B). Clinicians should refer newly diagnosed patients with an LGMD subtype and high risk of cardiac complications for cardiology evaluation even if they are asymptomatic from a cardiac standpoint (Level B). In patients with LGMD with a known high risk of respiratory failure, clinicians should obtain periodic pulmonary function testing (Level B). Clinicians should refer patients with muscular dystrophy to a clinic that has access to multiple specialties designed specifically to care for patients with neuromuscular disorders (Level B). Clinicians should not offer patients with LGMD gene therapy, myoblast transplantation, neutralizing antibody to myostatin, or growth hormone outside of a research study designed to determine efficacy and safety of the treatment (Level R). Detailed results and recommendations are available on the Neurology® Web site at Neurology.org.