Multimodal Evoked Potentials of Kennedy's Disease

Disentangling balance impairments in spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (Kennedy's disease) has been associated with balance dysfunction and falls. However, postural control has not been studied quantitatively. Here, we quantified upright stance and aimed to disentangle the role of vestibular, proprioceptive and oculomotor deficits. Static balance was assessed in Kennedy patients (n = 7) during quiet stance on a force platform under different visual and proprioceptive feedback conditions. Vestibular function was assessed with the video head impulse test. Sural nerve neurography was employed to evaluate the severity of peripheral neuropathy. Also, horizontal saccades were recorded and quantified by the main sequence relationship. Posturographic analyses revealed significantly increased body sway, more pronounced in conditions with closed eyes, which was also reflected in the calculated Romberg indices. Horizontal vestibulo-ocular reflex gains were normal, i.e. > 0.75. In contrast, compound sensory nerve action potentials were markedly decreased in all patients (mean = 2.4 μV). Two patients showed slow saccades with increased exponential main sequence constants. We conclude that Kennedy patients exhibit severe deficits in quiet stance. Postural instability is greatest in conditions of absent vision with reduced proprioception being the main determinant of unsteadiness. Some patients show slowed saccadic eye movements suggesting a nuclear abducens neuronopathy.

Unimpaired Neuropsychological Performance and Enhanced Memory Recall in Patients with Sbma: A Large Sample Comparative Study

Peculiar cognitive profile of patients with SBMA has been described by fragmented literature. Our retrospective study reports the neuropsychological evaluations of a large cohort of patients in order to contribute towards the understanding of this field. We consider 64 neuropsychological evaluations assessing mnesic, linguistic and executive functions collected from 2013 to 2015 in patients attending at Motor Neuron Disease Centre of University of Padova. The battery consisted in: Digit Span forwards and backwards, Prose Memory test, Phonemic Verbal fluency and Trail making tests. ANCOVA statistics were employed to compare tests scores results with those obtained from a sample of healthy control subjects. Multiple linear regressions were used to study the effect on cognitive performance of CAG-repeat expansion, the degree of androgen insensitivity and their interaction to cognitive performance. Statistical analyses did not reveal altered scores in any neuropsychological tests among those adopted. Interestingly, patients performed significantly better in the Prose Memory test's score. No relevant associations were found with genetic, hormonal or clinical patients' profile. Results inconsistent with previous studies have been interpreted according to the phenomenon of somatic mosaicism. We suggest a testosterone-related and the mood state-dependant perspectives as two possible interpretations of the enhanced performances in the Prose Memory test. Further studies employing more datailed tests batteries are encouraged.

Kennedy disease (X-linked recessive bulbospinal neuronopathy): A comprehensive review from pathophysiology to therapy

Kennedy's disease, also known as spinal and bulbar muscular atrophy (SBMA), is a rare, adult-onset, X-linked recessive neuromuscular disease caused by expansion of a CAG repeat sequence in exon 1 of the androgen receptor gene (AR) encoding a polyglutamine (polyQ) tract. The polyQ-expanded AR accumulates in nuclei, and initiates degeneration and loss of motor neurons and dorsal root ganglia. While the disease has long been considered a pure lower motor neuron disease, recently, the presence of major hyper-creatine-kinase (CK)-emia and myopathic alterations on muscle biopsy has suggested the presence of a primary myopathy underlying a wide range of clinical manifestations. The disease, which affects male adults, is characterized by muscle weakness and atrophy localized proximally in the limbs, and bulbar involvement. Sensory disturbances are associated with the motor phenotype, but may be subclinical. The most frequent systemic symptom is gynecomastia related to androgen insensitivity, but other abnormalities, such as heart rhythm and urinary disturbances, have also been reported. The course of the disease is slowly progressive with normal life expectancy. The diagnosis of SBMA is based on genetic testing, with 38 CAG repeats taken as pathogenic. Despite several therapeutic attempts made in mouse models, no effective disease-modifying therapy is yet available, although symptomatic therapy is beneficial for the management of the weakness, fatigue and bulbar symptoms.

Brain MR diffusion tensor imaging in Kennedy's disease

INTRODUCTION

Kennedy's disease (KD) is a progressive degenerative disorder affecting lower motor neurons. We investigated the correlation between disease severity and whole brain white matter microstructure, including upper motor neuron tracts, by using diffusion-tensor imaging (DTI) in eight patients with KD in whom disease severity was evaluated using the Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS).

METHODS

From DTI acquisitions we obtained maps of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (L1) and radial diffusivities (L2, L3). We then employed tract-based spatial statistics (TBSS) to investigate within-patient correlations of DTI invariants with ALSFRS and disease duration (DD).

RESULTS

We found a significant correlation between low ALSFRS and 1) low FA values in association commissural and projection fibers, and 2) high L3 values in commissural tracts and fronto-parietal white matter. Additionally, we found a significant association between longer DD and 1) low FA in the genu and body of corpus callosum, association fibers and midbrain and 2) high L1 in projection and association tracts.

CONCLUSIONS

The associations between clinical variables and white matter microstructural changes in areas thought to be spared by the disease process support the hypothesis of a multisystem involvement in the complex pathogenic mechanisms responsible for the clinical disability of these patients.

Theory of mind, empathy and neuropsychological functioning in X-linked spinal and bulbar muscular atrophy: a controlled study of 20 patients

Recent studies have described brain involvement, mainly at frontal level, in patients with spinal and bulbar muscular atrophy (SBMA), a rare adult-onset motor neuron disease caused by a CAG repeat in the androgen receptor (AR) gene. The aim of our research was to investigate the poorly characterized neuropsychological and psychological profile of these patients, on the basis of previous literature. We administered a neuropsychological screening and tests relating to cognitive and affective empathy, attributed to the theory of mind (ToM) framework, to 20 males with SBMA, and to age- and education-matched controls. Although patients' neuropsychological performance was unimpaired, a clear dissociation emerged between their cognitive and affective empathy. Patients had distinctive deficits in mentalizing, as assessed with the Faux Pas Test, whilst affective empathy (i.e., sharing experience), assessed with the Reading the Mind in the Eyes test, appeared to be preserved. The likely implications of subtle frontal lobe impairments on the one hand, and a protective influence of androgen insensitivity in these patients on the other, are discussed in the light of our results.

Cerebral involvement in spinal and bulbar muscular atrophy (Kennedy's disease): a pilot study of PET

OBJECTIVE

To investigate possible cerebral involvement in patients with spinal and bulbar muscular atrophy (SBMA) by (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET).

DESIGN

Ten patients with molecularly-confirmed SBMA and 5 age- and gender-matched healthy controls were recruited for brain FDG-PET studies. The data were analyzed and compared using the statistical parametric mapping (SPM) method.

RESULTS

Glucose hypometabolism in frontal areas of the cerebrum was found in patients with SBMA. However, no significant correlation with clinical variables, such as CAG repeat length, age at onset, or serum testosterone levels, was noted.

CONCLUSIONS

The perturbation of cerebral glucose metabolism in patients with SBMA argues against SBMA being a pure lower motor and sensory neuron syndrome. Mutations in the androgen receptor gene might have a more widespread effect in the cerebrum than previously recognized.

Perspectives of Kennedy's disease

Kennedy's disease, also known as bulbospinal muscular atrophy (BSMA), is a rare, adult-onset, X-linked, recessive trinucleotide, polyglutamine (poly-G) disorder, caused by expansion of an unstable CAG-tandem-repeat in exon 1 of the androgen-receptor (AR) gene on chromosome Xq11-12. Poly-Q-expanded AR accumulates in nuclei, undergoes fragmentation and initiates degeneration and loss of motor neurons and dorsal root ganglia. Phenotypically, patients present with weakness and wasting of the facial, bulbar and extremity muscles, sensory disturbances, and endocrinological disturbances, such as gynecomastia and reduced fertility. In the limb muscles weakness and wasting may be symmetric or asymmetric, proximal or distal, or may predominate at the lower or upper limb muscles. There may be mild to severe hyper-CK-emia, elevated testosterone or other sexual hormones, abnormal motor and sensory nerve conduction studies, and neuropathic or rarely myopathic alterations on muscle biopsy. BSMA is diagnosed if the number of CAG-repeats exceeds 40. No causal therapy is available but symptomatic therapy may be beneficial for weakness, tremor, endocrinological abnormalities, muscle cramps, respiratory failure, or dysphagia. The course is slowly progressive and the ability to walk lost only late in life. Only few patients require ventilatory support and life expectancy is only slightly compromised.

Distribution of androgen receptor mRNA expression in vocal, auditory, and neuroendocrine circuits in a teleost fish

Across all major vertebrate groups, androgen receptors (ARs) have been identified in neural circuits that shape reproductive-related behaviors, including vocalization. The vocal control network of teleost fishes presents an archetypal example of how a vertebrate nervous system produces social, context-dependent sounds. We cloned a partial cDNA of AR that was used to generate specific probes to localize AR expression throughout the central nervous system of the vocal plainfin midshipman fish (Porichthys notatus). In the forebrain, AR mRNA is abundant in proposed homologs of the mammalian striatum and amygdala, and in anterior and posterior parvocellular and magnocellular nuclei of the preoptic area, nucleus preglomerulosus, and posterior, ventral and anterior tuberal nuclei of the hypothalamus. Many of these nuclei are part of the known vocal and auditory circuitry in midshipman. The midbrain periaqueductal gray, an essential link between forebrain and hindbrain vocal circuitry, and the lateral line recipient nucleus medialis in the rostral hindbrain also express abundant AR mRNA. In the caudal hindbrain-spinal vocal circuit, high AR mRNA is found in the vocal prepacemaker nucleus and along the dorsal periphery of the vocal motor nucleus congruent with the known pattern of expression of aromatase-containing glial cells. Additionally, abundant AR mRNA expression is shown for the first time in the inner ear of a vertebrate. The distribution of AR mRNA strongly supports the role of androgens as modulators of behaviorally defined vocal, auditory, and neuroendocrine circuits in teleost fish and vertebrates in general.

Phenotypic differences in a large family with Kennedy's disease from the Middle Black Sea region of Turkey

We report the clinical and electrophysiological features of a large Turkish family with genetically confirmed X-linked spinal and bulbar muscular atrophy (SBMA). Family members were identified by field work. A detailed history was obtained from each subject, and each subject received a detailed neurological examination. To confirm the CAG repeat expansion in the AR gene, genomic DNA was extracted from the peripheral blood of patients. The family consisted of 128 individuals over five generations, with two consanguineous parents, one slightly affected female, and 12 affected males with SBMA. We studied the five surviving male patients and one surviving female carrier. The age at disease onset, phenotypic features, and disease severity varied among the family members. DNA analysis was performed on five individuals, belonging to five generations of the family. Four affected males and a slightly affected female carrier were shown to carry an expanded CAG repeat in the androgen receptor gene. This family report is consistent with previous studies suggesting that SBMA may be present with a wide clinical spectrum in affected family members. Further descriptions of SBMA affected families with different ethnic backgrounds may assist in identifying possible phenotypic and genetic features of the disease.

Rare association of antisynthetase syndrome and Kennedy's disease

Antisynthetase syndrome is a type of Idiopathic Inflammatory Myopathy (IIM) associated with anti-Jo1 antibody. Kennedy's disease or X-linked spinal and bulbar muscular atrophy (SBMA) is a rare neuromuscular disease. We describe the case report of a 53-year-old man who presented with proximal muscle weakness and a history of bilateral hand tremor. Initial physical examination demonstrated "mechanic's hands", Raynaud's phenomenon, having elevated creatine kinase and lactate dehydrogenase levels and anti-Jo1 antibody positivity. His muscle biopsy demonstrated inflammatory infiltrate characteristic of IIM. Considering these findings, we reached the diagnosis of antisynthetase syndrome and commenced immunosuppressive therapy. On follow-up examination, he had developed dysphagia, and his tremor had worsened. His electroneurogram result was characteristic of Kennedy's disease, and the genetic test result showed an allele with 44 CAG repeat expansion in the androgen receptor gene of the X chromosome. This confirmed that in addition to antisynthetase syndrome, he also had Kennedy's disease. This patient now receives immunology and neurology follow-up. His symptoms have improved with low dose corticosteroids, propranolol for tremor, vitamin B supplementation, and physiotherapy. This article presents a rare case report of a patient with concurrent antisynthetase syndrome and Kennedy's disease, both of which lead to elevated creatine kinase levels and muscle weakness, thus, underpinning the importance of careful follow-up of patients with IIM and maintaining an open mind to other diagnoses when faced with refractory and/or new symptoms.