Finger-nose inaccuracy means that the patient is asked to extend the arm and touch the fingertip of the examiner’s finger, and then point to the tip of his or her own nose, and repeat the comparison several times with different directions, speeds, and eyes open and closed. In the case of cerebellar lesions, the nasal finger is not accurate, the movement becomes slower when approaching the tip of the nose, the distance cannot be adjusted correctly, the distance is over-measured (poor distance discrimination) or there is motor tremor. The degree of nasal inaccuracy is parallel to the degree of lesion. Spinal cerebellar degeneration (spinocerebellarataxia) is a disease in which movement disorders are the main symptom and pathology is based on degeneration of the cerebellum and its afferent and efferent pathways, and clinically it is characterized by limb ataxia and dysarthria. What are the common causative factors of inaccurate finger noses? The doctor will first determine whether the patient has a neurological disorder of the cerebellum and spinal cord based on a clinical examination of the cerebral nervous system, then ask about his family history (including deceased relatives), and finally determine whether the patient has microcephaly through magnetic resonance imaging (MRI) and genetic testing. Because this is an autosomal dominant disease, if one parent has microcephaly, there is a 50% chance that their child will develop the disease regardless of gender. If the child is not genetically predisposed, the next generation will not develop the disease. A large number of clinical reports show that most patients with microcephaly are hereditary, and the disease is chronic and progressive, and if not effectively controlled, it will soon become life-threatening. Therefore, once detected, early medication should be used to effectively control the disease, improve the original symptoms, improve the quality of life, and delay life.