EXPLORATIVE STUDY OF SPINOCEREBELLAR ATAXIA 3: GENETIC AND CLINICAL ANALYSIS
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Date
2023-05-19
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Abstract
This study aims to explore the phenotype and genotype aspects of a family with
SCA3. This book contains eight chapters. Chapter 1 presents the background on
SCA3 that the research addresses and the pathomechanism and any issues related
to SCA3 disease investigated in this study.
In Chapter 2, three index patients with SCA3 from different families are evaluated.
The patients had the same polyQ stretch length, yet the clinical profiles, progression
of symptoms, and worsening of their condition over time were considerably
different. These symptoms included ataxia, speech problems, peripheral motor and
sensory nerve complaint, and cognitive impairment. Patients therefore presented
with a wide variety of symptoms and clinical features when SCA3 first manifested.
Chapter 3 describes the clinical profile of five subjects from the same family
with an ATXN3 mutation with expanded CAG repeat showing a broad range of
manifestations. All patients with SCA3 had prominent non-ataxia features besides
ataxia signs. Subjects with the prodromal stage showed a less severe disease with
only nystagmus, the symptom of peripheral nerve abnormalities, and mild cognitive
impairment (CI). Subjects with the ataxic stage of SCA3 had more extensive
neurological manifestations, including the cerebellar, extrapyramidal, pyramidal,
oculomotor, peripheral nerve symptoms, and mild CI.
The non-motor symptoms of SCA3 include peripheral nerve symptoms and cognitive
impairment. In Chapter 4, four subjects from the same family tree are examined
with abnormalities in the peripheral nerve, presenting with symptoms but with
or without clinical signs. Peripheral nerve abnormalities already shown in the
prodromal stage are also discussed. Nerve Conduction Study (NCS) analysis showed
a varied peripheral nerve involvement, including the axonal and demyelinating
lesion in sensory, motor, and motor nerves. Chapter 5 reports the peripheral neuropathy of one patient with SCA3 who experienced peripheral nerve symptoms preceding gait symptoms. However, the
sensory examination was normal, even when the NCS revealed axonal demyelinating
sensory-motor peripheral neuropathy. Chapter 6 discusses cognitive impairment consisting of general and cerebellar
cognitive function of patients with SCA3. Fifteen subjects from the same family tree
had their MMSE and MoCA-INA scores examined. The results show that the general
cognitive function in SCA3 subjects tended to be lower than that of normal subjects.
Then, seven subjects underwent further CCAS examination and showed impairment
in executive function (cognitive flexibility), attention (short-term memory), language
(verbal fluency), and memory (immediate memory). In the subjects with SCA3, the
cognitive function was more likely affected by the pathological disease process
rather than age and education level.
The involvement of the brain region that resulted in the abnormality of the motor
and cognitive function was shown in the brain MRI volumetry findings. In Chapter
7, seven subjects who underwent an MRI examination are discussed. This research
found a decrease in corpus callosum volume and cerebellum lobules I-II as well as
lobule IX, which control motor function and cognition, respectively.
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Keywords
Spinocerebellar, Ataxia, Type 3