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Polyneuropathy has been reported in cerebrotendinous xanthomatosis (CTX), although its nature and possible association with certain genotypes and phenotypes are unclear. The effect of chronic administration of chenodeoxycholic acid (CDCA) on peripheral nerve conduction parameters is still debated. We report clinical, laboratory, and electrophysiological findings in 35 CTX patients. Twenty-six subjects (74.2 %) showed peripheral nerve abnormalities. Polyneuropathy was predominantly axonal (76.9 % of patients) and generally mild. No correlation was found between its presence and clinical or biochemical data. In polyneuropathic patients, CDCA treatment improved electrophysiological conduction parameters, irrespective of the duration of therapy. Improvement mainly concerned nerve conduction velocities, whereas most nerve amplitudes remained unchanged. This means that CDCA treatment did not influence the number of axons activated by maximum electrical stimulation but increased the conduction of the still-excitable fibers. Our findings may suggest that CDCA treatment promotes myelin synthesis in nerve fibers with residual unaffected axons. The effect of therapy may therefore depend largely on the extent of irreversible structural damage to axons

Cerebrotendinous xanthomatosis (CTX) is known to be associated with osteoporosis and a higher incidence of bone fractures. However, the underlying pathogenesis is still unknown, and the effects of longterm replacement therapy with chenodeoxycholic acid (CDCA) on bone mineral density (BMD) have not been fully investigated. We studied 11 CTX patients aged 13–43 years. We performed dual-energy X-ray absorptiometry and assessed serum cholestanol and 25-hydroxyvitamin D (25-OHD) concentrations both at the time of diagnosis and after long-term treatment with CDCA. At baseline, we found low BMD in nine patients, cholestanol elevation in all subjects, and 25-OHD decrease in nine. After a mean follow-up time of 30 months (range 24–36), no substantial clinical changes including bone fractures occurred; and we detected a significant increase of both planar and volumetric BMD as well as normalization of plasma cholestanol levels and increase of serum 25-OHD. Densitometric improvement following CDCA introduction was not correlated to changes of biochemical parameters. Our study confirms the presence of low bone mass in CTX and demonstrates that longterm CDCA treatment increases bone mineral content. In this respect, improvement of vitamin D intestinal absorption secondary to bile acid restoration could play an important role. Moreover, our data strongly suggest the utility of periodic bone density evaluation in CTX patients.

Cerebrotendinous xanthomatosis (CTX) is a rare neurometabolic disease due to defective activity of sterol 27-hydroxylase, with plasma and tissue cholestanol storage. Clinical phenotype is characterized by both systemic manifestations and neurological signs. Therapy with chenodeoxycholic acid (CDCA) suppresses abnormal bile acid synthesis. The purpose of the study was to assess the frequency and clinical relevance of spasticity in the CTX phenotype and to study the usefulness of transcranial magnetic stimulation (TMS) in detecting corticospinal tract damage and monitoring the effects of replacement therapy. Twenty-four CTX patients underwent clinical evaluation including general disability scores, pyramidal and cerebellar function scales, assessment of serum cholestanol and TMS. Nine patients who started CDCA therapy at baseline received clinical and neurophysiological follow up. All patients showed signs of pyramidal damage which were relevant for clinical disability in 18 out of 24 cases (75%), resulting in spastic paraparesis. TMS revealed corticospinal alterations even in subjects with mild clinical signs of corticospinal tract involvement. After CDCA treatment, serum cholestanol decreased to normal concentrations in all patients. Clinical picture was unchanged in seven out of nine cases; in two others pyramidal signs disappeared. A reduction in abnormal neurophysiological parameters was found. Spastic paraparesis is the most frequent and relevant neurological feature in CTX patients. Replacement treatment with CDCA can prevent the progression of pyramidal damage, especially if started early in the course of the disease. TMS represents a sensitive indicator of corticospinal tract dysfunction and subclinical improvements in pyramidal function after CDCA therapy.