Spastic paraplegia, ataxia, mental retardation (SPAR): a novel genetic disorder.

OBJECTIVE: To describe a kindred with a dominantly inherited neurologic disorder manifested either as uncomplicated spastic paraplegia or ataxia, spastic paraplegia, and mental retardation. METHODS: Neurologic examinations and molecular genetic analysis (exclusion of known SCA and HSP genes and loci; and trinucleotide repeat expansion detection [RED]) were performed in six affected and four unaffected subjects in this family. MRI, electromyography (EMG), and nerve conduction studies were performed in three affected subjects. RESULTS: The phenotype of this dominantly inherited syndrome varied in succeeding generations. Pure spastic paraplegia was present in the earliest generation; subsequent generations had ataxia and mental retardation. MRI showed marked atrophy of the spinal cord in all patients and cerebellar atrophy in those with ataxia. Laboratory analysis showed that the disorder was not caused by mutations in genes that cause SCA-1, SCA-2, SCA-3, SCA-6, SCA-7, SCA-8, and SCA-12; not linked to other known loci for autosomal dominant ataxia (SCA-4, SCA-5, SCA-10, SCA-11, SCA-13, SCA-14, and SCA-16); and not linked to known loci for autosomal dominant hereditary spastic paraplegia (HSP) (SPG-3, SPG-4, SPG-6, SPG-8, SPG-9, SPG-10, SPG-12, and SPG-13) or autosomal recessive HSP SPG-7. Analysis of intergenerational differences in age at onset of symptoms suggests genetic anticipation. Using RED, the authors did not detect expanded CAG, CCT, TGG, or CGT repeats that segregate with the disease. CONCLUSIONS: The authors describe an unusual, dominantly inherited neurologic disorder in which the phenotype (pure spastic paraplegia or spastic ataxia with variable mental retardation) differed in subsequent generations. The molecular explanation for apparent genetic anticipation does not appear to involve trinucleotide repeat expansion.

Evaluation of blink reflex results obtained from workers previously diagnosed with solvent-induced toxic encephalopathy.

We reviewed blink reflexes recorded from 51 railroad workers with long-term occupational exposure to solvents who were diagnosed by others with solvent-induced toxic encephalopathy. No worker fulfilled conventional clinical criteria for dementia or trigeminal mononeuropathy. All workers had normal R1 and R2 blink reflex latencies. R1 latencies correlated significantly with several nerve conduction measures, including F wave latencies, suggesting that some intersubject variability reflected intrinsic conduction properties, not isolated brain-stem function. Although normal, the workers' R1 latencies were significantly prolonged compared with historical control groups, including gender-matched control subjects of similar mean age (11.2 ms vs 9.9 ms; P < 0.0001). Stepwise multiple regression models demonstrated significant associations of R1 latency with age and use of CNS-active prescription medications (P = 0.003), but duration of occupational solvent exposure did not enter into the models. Paradoxically, workers using CNS-active medications had significantly shorter R1 latencies compared with workers not using such medications (10.9 vs 11.7 ms; P = 0.01). Job title, another potential surrogate measure of exposure, was not significantly related to reflex latencies. The geographical site of predominant solvent exposure did influence R1 latency, and workers from one site had longer exposure duration and longer R1 latencies than remaining workers. However, an interaction between age and exposure duration (r = 0.39; P = 0.003) confounded interpretation of this observation. Disability or work status, mental status findings, or classification of encephalopathy did not influence blink reflex latencies. The overall results do not support, but do not entirely exclude, a possible relationship between subclinical blink reflex abnormalities and occupational exposure to solvents. Nevertheless, it is clear from these results that the small group differences in R1 latency between exposed workers and control subjects are of no diagnostic importance and of uncertain physiologic importance, and they may reflect unrecognized confounders and technical factors.

Granulomatous myositis, primary biliary cirrhosis, pancytopenia, and thymoma.

Granulomatous myopathies are rare. Most cases are associated with sarcoidosis. We report a case of granulomatous myopathy associated with primary biliary cirrhosis, pancytopenia, and thymoma. The literature in regard to granulomatous myopathy and its pathogenesis is reviewed. Intermittent pulsed intravenous methylprednisolone may be useful as maintenance therapy for granulomatous myopathy and other neuromuscular syndromes for patients intolerant of oral corticosteroids.

The effects of toxins on muscle.

Substances known to be myotoxic are reviewed, including descriptions of the resultant clinical syndromes and the mechanisms important in their development. Certain host characteristics such as altered immune and metabolic regulation are known to modulate the effects of individual myotoxins, producing varied clinical syndromes. Evaluation procedures important in identifying a toxin-induced myopathy are described.

Neurologic evaluation of workers previously diagnosed with solvent-induced toxic encephalopathy.

We examined 52 railroad workers with long-term occupational solvent exposures (average 22 years duration) who had been previously diagnosed by others as having solvent-induced toxic encephalopathy. All described episodes of transient intoxication associated with occupational solvent exposure. Persistent symptoms developed, an average, 16 years after exposure onset and included impaired memory (38), altered mood (21), imbalance (18), and headache (17). Thirteen workers had mild mental status abnormalities, but none fulfilled conventional clinical criteria for encephalopathy or dementia. None had abnormal blink reflex (51) or abnormal electroencephalographic (39) studies. Eight of 47 magnetic resonance imaging studies showed evidence of scattered ischemic lesions among workers with known diabetes mellitus (2), elevated blood pressure (4), or peripheral vascular disease (2). One magnetic resonance imaging scan showed mild cortical atrophy. In stepwise multiple linear and logistic regression models, no statistically significant (P < 0.05) dose-response relationships were found between exposure duration and symptoms or signs that were suggestive of encephalopathy. However, the number of symptoms (P < 0.001) and the number of signs (P = 0.05) were associated with current use of central nervous system-active medications. Further, lower Mini-Mental Status Examination scores were associated with a history of alcohol abuse (P = 0.01) and lower educational level (P = 0.03). The number of chief symptoms involving memory, mood, balance, or headache differed significantly among workers in different geographic sites (F(3.48) = 2.94, P = 0.04), a finding that was not explained by job title or exposure duration. There also was a significant (P = 0.0001) inverse relationship between initial exposure year (r2 = 0.60) or total years of exposure through 1987 (r2 = 0.56) and interval to major neurologic symptom onset, suggesting that factors other than solvent exposure account in part for worker complaints. We found no objective neurologic evidence supportive of toxic encephalopathy or any other uniform syndrome among these individuals, and most complaints were explained by neuropsychological factors or conditions unrelated to occupational solvent exposure.

Absence of polyneuropathy among workers previously diagnosed with solvent-induced toxic encephalopathy.

An association between polyneuropathy and occupational exposure to trichloroethylene, trichloroethane, perchloroethylene, or similar solvents alone or in combination is controversial. We sought to determine whether workers previously diagnosed with solvent-induced toxic encephalopathy had objective evidence of polyneuropathy. Thirty railroad workers previously diagnosed with toxic encephalopathy were examined in the context of litigation against their employers. All described long-term occupational solvent exposure averaging 20 years in duration (range, 10 to 29 years) and producing acute intoxication on a regular basis. The diagnosis of subclinical or clinical polyneuropathy was established using a combination of symptoms, signs, and nerve conduction study (NCS) measures, consistent with standard clinical practice. Potential confounders were identified. NCS results were compared with historical controls, including unexposed workers matched by gender, age, and body mass index. Dose-response relationships were evaluated using simple linear and stepwise regression models. Three workers fulfilled clinical polyneuropathy criteria. The only worker fulfilling NCS criteria for confirmed clinical polyneuropathy had diabetes mellitus. Mean NCS values for most measures were similar to control values, and existing differences in sensory amplitudes disappeared when compared with the matched control group. NCS measures were not significantly influenced by exposure duration or job title. Separation into groups on the basis of the presence or absence of polyneuropathy symptoms, previous diagnosis of polyneuropathy, disability status, and severity or type of encephalopathy did not demonstrate significant NCS differences. The complaints of these workers claiming neurotoxic injury from occupational solvent exposure are not explained by peripheral nervous system dysfunction.

Acute effects of adrenergic-mediated ischemia on nerve conduction in subjects with type 2 diabetes.

Several lines of evidence support peripheral nerve ischemia as a contributing factor in the etiology of human diabetic neuropathy. We questioned whether diabetic subjects with relatively normal nerve function in the baseline state would be more likely than healthy control subjects to show either improvement of ulnar nerve function with acute intraarterial infusion of nitroprusside (vasodilation) or be more sensitive than control subjects to worsening of nerve function with acute intraarterial infusion of norepinephrine (vasoconstriction). We measured forearm blood flow (FABF) using venous occlusion plethysmography and assessed ulnar nerve function at baseline and during two intrabrachial artery infusions. Six nondiabetic control subjects (mean age, 56 years) and 11 subjects with type 2 diabetes (mean age, 58 years) in good general health participated. Only three type 2 diabetic subjects had peripheral sensory neuropathy, which was mild. Among control subjects, there was no significant change in sensory distal latency, motor distal latency, motor proximal latency, or sensory or motor conduction velocity during norepinephrine infusion. In contrast, among type 2 diabetic subjects, there was a significant increase in sensory (baseline vnorepinephrine, 2.73+/-0.10 v 2.94+/-0.10 milliseconds [MS], P< or =.01) and motor distal latencies (baseline v norepinephrine, 2.90+/-0.06 v 3.18+/-0.1 ms, P< or =.001) and motor proximal latency (baseline v norepinephrine, 7.15+/-0.18 v 7.60+/-0.23 ms, P<.01) and a decrease in sensory conduction velocity (baseline v norepinephrine, 52.1+/-2.0 v 47.7+/-1.6 m/s, P<.01) during norepinephrine infusion. There were no consistent changes in nerve function during nitroprusside infusion in either group. In summary, we found that subjects with type 2 diabetes, but not control subjects, demonstrate a decrement in nerve function with vasoconstriction during intraarterial infusion of norepinephrine, but no consistent change during nitroprusside-induced vasodilation. These findings suggest there may be enhanced sensitivity of nerve function to ischemia in type 2 diabetic subjects with mild or absent clinical neuropathy.

Juvenile myasthenia gravis: treatment with immune globulin and thymectomy.

Juvenile myasthenia gravis is rare, representing just 10% of all myasthenia gravis. Treatment of the juvenile form is similar to the adult form, although concerns of long-term side effects limit use of immunomodulators and thymectomy in children, especially the very young. We review the clinical course of three children with juvenile myasthenia gravis, as well as the current status of intravenous immunoglobulin and thymectomy as treatments for juvenile myasthenia gravis.

Chronic inflammatory demyelinating polyradiculoneuropathy in children: II. Long-term follow-up, with comparison to adults.

We previously reviewed the presentation, initial clinical course, and electrodiagnostic features of children with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). We now report the long-term follow-up of 12 children with idiopathic CIDP, and compare these to 62 adults with idiopathic CIDP. Children often had more rapidly fluctuating courses than adults. A relapsing course was significantly more common in children than in adults. The recovery of children from each episode of deterioration was usually excellent, and better, on average, than in adults. Ventilatory support was never required for children with slowly evolving illness; only 2 children with a precipitous onset clinically resembling Guillain-Barré syndrome required ventilatory support. Prednisone, plasma exchange, and intravenous immunoglobulin (IVIg) usually were effective in children. Multiple courses of IVIg could be given with continued efficacy. Treatment often could be discontinued in children with relapsing courses. The prognosis for children was excellent. Adults demonstrated a good, but more variable, outcome.

Clinical features of perineuritis.

We report 13 patients with pathologically confirmed perineuritis. Seven patients had diabetes mellitus, 5 had nutritional abnormalities, 2 had associated rheumatological illnesses, 2 had sepsis with multiorgan failure, and 1 had a history of malignancy. Electrophysiologic testing demonstrated mononeuritis multiplex in 7, demyelinating neuropathy in 4, distal sensory and motor neuropathy in 1, and polyradiculoneuropathy in 1. Twelve patients received immunomodulating therapy with variable responses. We conclude that perineuritis is associated with a number of different systemic conditions and several clinical patterns of peripheral neuropathy. Response to immunomodulation is variable. The most frequent association is with diabetes mellitus, a previously unrecognized association.

Collet-Sicard syndrome mimicking neuralgic amyotrophy.

A man with shoulder pain, wasting, and weakness had ipsilateral cranial nerve abnormalities. Electrodiagnostic studies supported a diagnosis of neuralgic amyotrophy, but we later demonstrated a spinal accessory mononeuropathy with ipsilateral hypoglossal weakness (Collet-Sicard syndrome). Magnetic resonance imaging demonstrated an inaccessible occipital condyle mass, and disseminated adenocarcinoma was subsequently diagnosed. Although cranial mononeuropathies can occur in neuralgic amyotrophy, this case illustrates the importance of identifying a focal lesion, and highlights the localizing value of electrodiagnosis.

Randomized trial of azathioprine or prednisone for initial immunosuppressive treatment of myasthenia gravis.

Ten patients with myasthenia gravis were randomized to azathioprine or prednisone as the initial immunomodulating drug and followed for over one year. Of five patients randomized to azathioprine, two had idiosyncratic reactions and were immediately crossed over to prednisone. Two patients completed one year on azathioprine with little or no change in level of function and were crossed over to prednisone and showed greater improvement. The fifth patient on azathioprine had a satisfactory improvement and continued on it during the second year. All patients initially randomized to prednisone improved, but the degree varied among patients. The side effects of azathioprine were idiosyncratic reactions. The side effects of prednisone were manageable.

Chronic inflammatory demyelinating polyradiculoneuropathy in children: I. Presentation, electrodiagnostic studies, and initial clinical course, with comparison to adults.

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is rare in children. We reviewed features of 15 children with idiopathic CIDP, and compared these to 69 adults with idiopathic CIDP. Children demonstrated many similarities to adults: (1) Antecedent events were uncommon. (2) There was a high frequency of weakness and reflex loss, a relatively high frequency of sensory loss, and a low frequency of pain and cranial neuropathies. (3) Cerebrospinal fluid protein levels were usually elevated. (4) On electrodiagnostic testing, not all nerve segments were abnormal, and not all children satisfied electrodiagnostic criteria for CIDP. Children differed from adults with CIDP in several ways: (1) The onset of symptoms was usually more precipitous. (2) Gait abnormalities were a more frequent presenting symptom. (3) Children always presented with significant neurological dysfunction, and not with the minor symptoms initially seen in some adults. The initial response of children with CIDP to immunomodulating therapy was excellent.

Foot drop as a harbinger of aortic occlusion.

A man presented with foot drop and 2 months later an infrarenal occlusion of his abdominal aorta was discovered. Initial evaluation found no structural etiology for his nerve injury. His neurologic deficits progressed until gangrenous changes developed in his feet leading to the discovery of aortic occlusion. This case demonstrates that peripheral nerve injury in the legs may signal underlying large vessel occlusive disease. We discuss the localization and potential mechanisms of ischemic nerve injury.