Showing papers by "Bing-Wen Soong published in 2005"

Median nerve motor conduction velocity is concordant with myelin protein zero gene mutation.

Abstract: Myelin protein zero gene (MPZ) mutations may account for a small proportion of cases of Charcot-Marie-Tooth disease (CMT). Different MPZ mutations may be associated with different clinical and electrophysiological phenotypes. To expand our understanding of the characteristics of nerve conduction velocity (NCV) in patients with different MPZ mutations, the authors collected and analysed the NCV values from patients with MPZ mutations. The NCVs of fourteen patients from six families carrying MPZ mutations of Val58Asp, Ser63Phe, Thr65Ile,Arg98Cys, Arg98His, and Ser233fs were collected retrospectively. Five of them had received nerve conduction studies (NCS) twice. The mutations were verified by polymerase chain reaction (PCR) amplifications and nucleotide sequencing. Scatterplot analyses of median motor NCV (MNCV) versus specific MPZ mutation were performed. The median MNCV varied widely, with a mean of 16.3 m/s (SD=7.7 m/s) and a range of 5.1–32.9 m/s. Median MNCVs of patients with particular MPZ mutations were similar. Moreover, Median MNCV did not change significantly over time. There was concordance between median MNCV and specific MPZ mutations. However, median MNCV is not an ideal measure with which to distinguish CMT1B patients with MPZ mutations from CMT1A patients with PMP22 mutations.

Spastic paraparesis as a manifestation of metabolic vitamin B12 deficiency

Abstract: Sirs: Vitamin B12 deficiency may be associated with variable neurological symptoms, including peripheral neuropathy, myelopathy, altered mental status, optic neuropathy, and cerebellar ataxia [1–3]. The myelopathy caused by vitamin B12 deficiency is well known as subacute combined degeneration, which is characterized by lesions in the posterior and lateral columns, always leading to both sensory and motor deficits [4]. Here we describe a 39-year-old man who had metabolic vitamin B12 deficiency but low normal vitamin B12 serum levels and developed a spastic paraparesis without sensory impairment. The 39-year-old man had begun developing progressive spastic paraparesis without sensory symptoms 20 years previously. In the past two months, he had also suffered from sexual and urinary dysfunction with frequent nocturia, occasional urine incontinence, and absence of morning erection. His prenatal and developmental histories were normal. The family history was unremarkable. Neither gastrointestinal disease nor a history of nitrous oxide exposure could be traced. He had been a strict vegetarian because of religious faith since adolescence. Neurological examination revealed mild weakness, marked spasticity of lower limbs with a scissor gait, and hyperactive deep tendon reflexes with bilateral ankle clonus and extensor plantar responses. The mental status, cranial nerves, coordination, and sensory test, including modalities of pinprick, light touch, and proprioception were normal. Laboratory studies demonstrated a normal complete blood cell count, a serum vitamin B12 level of 195 ng/L (reference range 130–785 ng/L), and a folic acid level of 19.5 μg/L (3–17 μg/L). His serum homocysteine level was 30.59 μmole/L (5–14 μmole/L). The serum methylmalonyl acid level was not checked. The results of cerebrospinal fluid studies, including cell counts, glucose, protein, IgG index, oligoclonal banding, anti-HTLV1 antibody titer, and VDRL test, were normal. Serum VDRL and HIV tests, anti-parietal cell antibody titer, and copper level were normal. Magnetic resonance imaging of the brain and spinal cord, nerve conduction studies, and somatosensory evoked potentials of the median and tibial nerves were all normal. The patient was treated with intramuscular injections of cyanocobalamin 1 mg daily for 7 days, weekly for 3 weeks, and monthly thereafter. On the sixth day of therapy, the vitamin B12 serum level increased beyond 1200 ng/L and the serum homocysteine level normalized to 7.38 μmole/L. Three months later, lower limb weakness had recovered fully and spasticity became moderately improved. The nocturia and urinary incontinence disappeared, and he regained daily morning erection as well as a fair sexual function. Five months later, spasticity persisted and transcranial magnetic stimulation study still revealed a mildly prolonged central motor conduction time (Table 1). Spastic paraparesis is uncommon in patients with vitamin B12 deficiency. Healton et al. reported that only seven of 153 episodes of cobalamin deficiency with neurological findings were associated with spastic paraparesis, and all were accompanied by proprioceptive deficits [1]. Diagnosis of metabolic vitamin B12 deficiency in patients with low normal serum vitamin B12 level can be established by elevated serum methylmalonyl acid or homocysteine levels [5–7]. Both metabolites may accumulate when there is impairment of cobalamin-dependent metabolic pathways. In this patient, the diagnosis could be supported by clinical response to vitamin B12 therapy. Other differential diagnosis, including copper deficiency [8, 9], can be excluded by normal laboratory data. Familial spastic paraparesis cannot be totally excluded without a detailed family history but is less likely in light of the remarkable improvement with treatment. This case demonstrates the importance of taking into consideration metabolic vitamin B12 deficiency in people with a low normal serum cobalamin level. It also LETTER TO THE EDITORS