Arnold Syndrome refers to a structural problem affecting the brain, specifically the cerebellum and brainstem. This condition involves a defect in the formation of these brain regions. The malformation can interfere with the normal flow of fluids within the brain and spinal cord, creating pressure that affects function and leads to various neurological challenges.
What is Arnold Syndrome
Arnold Syndrome is more formally known as Chiari Malformation Type II, or Arnold-Chiari malformation. This condition is characterized by the downward displacement of the cerebellum, pons, medulla, and fourth ventricle, which are parts of the brain, through the foramen magnum, an opening at the base of the skull, and into the spinal canal. This anatomical issue can obstruct the normal flow of cerebrospinal fluid (CSF), which surrounds and protects the brain and spinal cord.
The displacement of these brain structures puts pressure on the brainstem and spinal cord, leading to a range of neurological symptoms. Chiari Malformation Type II is frequently associated with myelomeningocele, a severe form of spina bifida where the spinal cord and its covering do not close properly during fetal development. Almost all children born with myelomeningocele also have Chiari Malformation Type II, which can impact various bodily functions.
Causes and How it Develops
Arnold Syndrome is primarily a congenital condition, arising from developmental issues during fetal growth. The exact cause is not always known, but it is believed to involve a combination of genetic and environmental factors. Some research suggests that the base of the skull in affected individuals may not grow to a normal size before birth, leading to crowding of brain structures as the brain develops.
This mismatch between skull size and brain size can cause the cerebellar tonsils and sometimes the brainstem to be pushed downward into the spinal canal. While often congenital, Chiari malformations can be acquired later in life in rare instances due to factors such as injury, tumors, or fluid accumulation that alter pressure within the skull.
Recognizing the Symptoms
The symptoms of Arnold Syndrome, or Chiari Malformation Type II, can vary significantly depending on the extent of the malformation and the individual’s age. Headaches are common and may worsen with coughing, sneezing, or straining. Neck pain and stiffness, which can radiate to the shoulders and arms, are also frequently reported.
Individuals may experience problems with balance and coordination, leading to an unsteady gait and difficulty with fine motor skills. Numbness or tingling sensations in the hands and feet are common due to spinal cord compression. Other symptoms include dizziness, difficulty swallowing (dysphagia), blurred or double vision, and involuntary rapid eye movements (nystagmus). Less common symptoms are ringing in the ears (tinnitus), weakness in the arms and legs, and changes in speech.
In infants, symptoms often present differently and can include feeding difficulties, such as gagging, drooling, or vomiting. They may also exhibit irritability, head banging, noisy breathing, or short periods of not breathing (apnea). Weakness in the arms and developmental delays can also be observed in younger children. The presence of a syrinx, a fluid-filled cavity within the spinal cord, can lead to additional symptoms like muscle weakness, stiffness, and altered sensation to pain or temperature.
Diagnosis and Treatment Options
Diagnosing Arnold Syndrome begins with a neurological examination. The most definitive diagnostic tool is Magnetic Resonance Imaging (MRI) of the brain and spine. An MRI provides detailed images that can show the abnormal displacement of the cerebellum and brainstem into the spinal canal, as well as any associated conditions like hydrocephalus or a syrinx.
Treatment approaches for Arnold Syndrome depend on the severity of symptoms and the presence of associated conditions. For individuals with mild symptoms, conservative management may be considered, including pain medication for headaches and neck pain, and physical therapy for balance and coordination issues. If symptoms are severe or progressive, surgical intervention is often necessary.
The primary surgical procedure for Arnold Syndrome is posterior fossa decompression. This surgery aims to relieve pressure on the brainstem and spinal cord by creating more space at the base of the skull. It involves removing a small section of the bone at the back of the skull and sometimes the upper cervical vertebrae. If hydrocephalus, an accumulation of excess cerebrospinal fluid in the brain, is present, a shunt may be surgically implanted to drain the fluid and reduce pressure. The goal of these treatments is to alleviate symptoms, prevent further neurological damage, and improve the individual’s quality of life.