A Chiari malformation (Arnold Chiari Syndrome) refers to the descending of a section of the brain through an opening at the bottom of the skull. This cavity would usually be clear, and the blockage caused by the abnormally positioned tissue can cause a number of problems, including stopping the healthy flow of fluid – known as cerebrospinal fluid – along the spinal canal. The part of the brain affected is known as the cerebellar tonsils, in cases of Chiari malformation they protrude too low, reaching past the base of skull.
It was an Austrian pathologist named Hans Chiari, who first began to recognise patterns in a hitherto unconnected set of symptoms, in 1891. Three years later a second pathologist, the German Julius Arnold was performing an autopsy on a child, he too noticed deformations of the brain and gave an account of his findings, backing up those of Chiari. This led to the disorder being known as the Arnold-Chiari malformation.
Patients can be affected in many ways, some do not even realise they have the condition and some will only begin to suffer when they reach adolescence or young adulthood. Although in other cases of Arnold-Chiari syndrome, child carriers are affected too. The most common symptoms that patients present with are moderate to extreme headaches and neck pain. After that, many people will describe feelings of disorientation and dizziness, centred on the eye, ear and throat areas, subsequently, swallowing maybe difficult. There are often multiple aural disturbances and visual problems that can lead to vertigo or dizziness.
These are caused by a build up of pressure at the base of the skull which impacts on the brain and spinal cord, interrupting the normal flow of cerebrospinal fluid between the two. Consequently, activities which increase the stress on this area, such as coughing, laughing or taking part in exercise can exacerbate the problem in the short term. Furthermore, patients suffering with Arnold-Chiari malformations may find their fine motor skills are impaired, they could have general feelings of weakness in the muscles and often tire easily. Their extremities may be affected by tingling which causes pain, and they may experience heart palpitations.
The symptoms of Arnold –Chiari syndrome are relatively complex, and in the past, many patients may have found it hard to receive a swift and appropriate diagnosis. However, in recent years the number of reported cases has increased, this would suggest doctors are becoming more aware of the condition and more incline to offer a conclusive test. There are excellent scanning technologies available, most notably the use of MRI imaging. In cases of suspected Chiari malformation this is an invaluable diagnostic tool for medical professionals, as the characteristic abnormal brain growth can be easily recognised.
There are four types of Chiari malformations, most patients will be classified as having a type 1. Types 2, 3 and 4 refer to far more severe conditions. Often type 2 is present at birth and linked to spina bifida, children may have problems with breathing and in most cases there is an access of fluid on the brain – known as hydrocephalus.
Type 3 is very rare, it occurs when an infant’s skull has not completed fused together in the womb, resulting in a section of the brain lying outside of its head. Type 4 Chiari Malformations are again extremely uncommon, this condition is also one that manifests as a birth defect, and here the baby is born with an incomplete cerebellum – the part of the brain which is found at the back of the skull.
However, even within the mildest classification, type 1, there can be an escalation of the condition if it goes untreated. Over an extended period of time, the complications can lead to quite serious disabilities and more rarely, paralysis. For most sufferers the most common problem they will encounter is a condition known as syringomyelia. Here, the spinal cord is affected by the formation of a long cavity that fills with fluid, this tube-like structure is known as a syrinx. If left untreated it can grown and begin to compress the vital spinal structures, a patient may experience a lack of bladder or bowel control, pain and muscle weakness.
The treatment for a syrinx involves removing some of the built up pressure by draining away the fluid. Despite there being a risk of complications, this process is generally expected to halt the progressive nature of a syrinx and alleviate the patient’s symptoms.
Arnold-Chiari syndrome can also induce a secondary condition, the results of which can be irreversible. It is known as tethered cord and is caused by one end of the spinal cord becoming locked in place by the tissue surrounding it. The spinal cord performs a variety of essential functions, sending messages to and from the brain that travel around the body. In a normal spinal column, the cord floats freely within a bath of cerebrospinal fluid, however if the cord is constricted at one end it can become stretched and damaged.
The condition can be treated if it is noticed early enough, however the symptoms may not present until the patient begins to grow and the cord becomes strained. Once the cord is stretched in this way, it is possible for the bundle of nerves within to sustain permanent damage.
A patient suffering from a tethered cord may have difficulty with their mobility and continence. Less serious aspects of the condition can be pain that travels the length of the back and into the legs, and a sensation of numbness in these areas.
There are a number of surgical procedures that can help, these are undertaken in a bid to release the spinal cord from the connective tissue and are tailored to the severity of each case. Back up treatment will be aimed at alleviating the symptoms, providing pain relief and continence counselling along with physiotherapy. The care package will also include careful monitoring, to ensure the patients condition does not worsen over time.
The causes of Arnold-Chiari are not entirely understood, though it is known to begin during gestation.