Patient 1 is a 19-year-old female firstborn child of healthy, consanguineous parents. She had delayed developmental motor milestones and did not begin ambulating until the age of 3 years. Frequent falls, particularly during running, notably occurred during early childhood. At the age of 3 years, she developed ataxic gait and dysarthria that progressed over several years before plateauing; the number of falling episodes even decreased after the initiation of occupational therapy. At the time of examination, the patient was able to walk without any assistance. The patient performed normally at school and her cognitive function was normal according to Mini-Mental State Examination (score 30/30). She also complained of episodic muscle cramps, predominantly in the calf muscles. She neither had history of seizure, urinary or fecal incontinence, urinary urgency, nor audiologic, or visual problems. Neurologic examination at the age of 18 years demonstrated an ataxic gait with moderate dysarthria. Limb examination was significant for amyotrophy and pes cavus without any evidence of spasticity. Furthermore, bilateral sixth nerve palsies with saccadic pursuit and horizontal nystagmus were observed. In addition, mild rigidity after activation maneuvers (Supplementary Video 1), mirror movements (Supplementary Video 2), hypokinesia (Supplementary Video 3), and dysmetria were noticed in both upper extremities, predominantly on the left side. Although patellar reflexes were quite brisk, Achilles deep tendon reflexes, and deep tendon reflexes in the upper extremities were absent. Rapid elbow extension and supination of the forearm did not reveal any evidence of spasticity. Extensor plantar reflexes were present bilaterally (Babinski signs were present bilaterally). Nerve conduction studies and needle electromyography (EMG/NCS) were consistent with axonal sensorimotor polyneuropathy with some demyelinating features. Optical coherence tomography (OCT) revealed increased thickness of retinal nerve fiber layers (Figure 1). Echocardiography demonstrated myxomatous mitral valve leaflets without any evidence of hypertrophic cardiomyopathy. Pure tone audiometry and tympanometry were normal. Brain magnetic resonance imaging (MRI) depicted atrophy of the superior cerebellar vermis, thinning of the posterior mid-body of corpus callosum, bilateral parietal atrophy on T1-weighted images, bilateral hypointense stripes in the pons on T2/fluid-attenuated inversion recovery (FLAIR) sequences, bilateral hyperintensity of the lateral pons on coronal images on T2 sequences, and a hyperintense rim around both thalami on T2-weighted images (Figure 2). Laboratory investigations including serum vitamin B12, folate, vitamin E, thyroid function tests, anti-gliadin antibodies, lactate/pyruvate ratio, and blood and urine amino acid profiles were normal. After treating the patient with L-DOPA/benserazide 100/25 mg four times daily for 6 weeks, mild improvements in successive slowing and hesitation in finger tapping and hand movements were observed (Supplementary Videos 3-6). The patient also reported significant improvements in episodic muscle cramps during this period. Quality of life was assessed using the Persian version of the short form health survey (SF-36) before and 6 weeks after the treatment. Quality of life improved after the treatment from 54.85 to 57.42 with notable improvements in bodily pain and social functioning. She did not report any side effects during this 6-week period. The patient was also evaluated on two occasions after this period, and her motor function was assessed using Unified Parkinson's Disease Rating Scale III (UPDRS-III) on and 48 h off medication, which showed a decrease in UPDRS-III scores from 17 to 12 on L-DOPA (Supplementary Videos 7-20). As a result, the patient was maintained on L-DOPA therapy.