Question: What is (are) Chiari malformation type 1 ?
Answer: Chiari malformation type 1 is a structural abnormality of the cerebellum, the part of the brain that controls balance. It involves the extension of the lower part of the cerebellum into the foramen magnum (the large hole at the base of the skull which allows passage of the spinal cord), without involving the brainstem. Normally, only the spinal cord passes through this opening. This malformation is the most common type of Chiari malformation and may not cause any symptoms. Depending on the symptoms present and severity, some individuals may not require treatment while others may require pain medications or surgery.
Source: GARD

Question: What are the symptoms of Chiari malformation type 1 ?
Answer: What are the signs and symptoms of Chiari malformation type 1? The Human Phenotype Ontology provides the following list of signs and symptoms for Chiari malformation type 1. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Areflexia of upper limbs - Arnold-Chiari type I malformation - Autosomal dominant inheritance - Babinski sign - Basilar impression - Diplopia - Dysarthria - Dysphagia - Gait ataxia - Headache - Hearing impairment - Hyperacusis - Limb muscle weakness - Lower limb hyperreflexia - Lower limb spasticity - Nystagmus - Paresthesia - Photophobia - Scoliosis - Small flat posterior fossa - Syringomyelia - Tinnitus - Unsteady gait - Urinary incontinence - Vertigo - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.
Source: GARD

Question: What causes Chiari malformation type 1 ?
Answer: What causes Chiari malformation type 1? Primary or congenital Chiari malformations are caused by structural defects in the brain and spinal cord that occur during fetal development. The underlying cause of the structural defects are not completely understood, but may involve genetic mutations or lack of proper vitamins or nutrients in the maternal diet. Less frequently, Chiari malformation type 1 is acquired after birth. Causes of acquired Chiari malformation type 1 involve the excessive draining of spinal fluid from the lumbar or thoracic areas of the spine as a result of injury, exposure to harmful substances, or infection. Click here to view a diagram of the spine.
Source: GARD