Sensory ataxia is considered both a sign and a symptom in neurology. Sensory ataxia is a type of ataxia that is caused by the loss of natural sensory ability to the control the movement of the body. This means that an individual loses the sense of where different parts of the body are located in relation to each other and the ground. Sensory ataxia is a problem of incoordination as a result of a disruption of somatosensory feedback. It is the result of disruption of neuronal pathways that interfere with proprioception, particularly lesions involving dorsal nerve roots, medial lemniscus, peripheral nerves, and posterior columns.
Sensory ataxia is an impairment of one’s sense of position that causes uncoordinated walking or ataxia. It occurs when an individual loses proprioception, a natural sensory ability. An individual usually depends on proprioception to keep track of the body’s physical orientation in the ground or in space. When one loses proprioception, one cannot fully make up for the lack of information with input from vision and other senses. This results in symptoms of ataxia which may include poor body balance that gets worse in the dark or in poor light conditions and/or a stomping gait caused by inaccurate foot placement.
Sensory ataxia is often mistaken for cerebellar ataxia although cerebellar ataxia is more common and is easier to identify because of its symptoms that are not present in sensory ataxia. The syndromes of sensory ataxia-plus though may have a component of cerebellar ataxia. Romberg’s sign and pseudoathetosis are the unique symptoms of sensory ataxia that can distinguish them from other forms of ataxia.
Nystagmus or repetitive eye movements is one of the symptoms of cerebellar ataxia that is not present in sensory ataxia. Dysarthria or unclear articulation of speech is also another symptom of cerebellar ataxia that is not present in sensory ataxia. There is a staggering gait for cerebellar ataxia while there is an unsteady or high stepping/stamping gait for sensory ataxia. Both disorders have eye movement problems but with cerebellar ataxia, the eye movements are either normal or they tend to be slow but with sensory ataxia,
the eye movements are sometimes abnormal. The deep tendon reflexes are either normal or pendular for cerebellar ataxia while they may either be present or absent for sensory ataxia. The joint position sense is normal for cerebellar ataxia while it is impaired for sensory ataxia. The exteroceptive sensation is normal for cerebellar ataxia while it is reduced for sensory ataxia. Both forms of ataxia though experience or manifest symptoms of finger-nose ataxia where it is significantly worse with eye closure for someone who has sensory ataxia. Both ataxia disorders also experience heel-shin ataxia which is also significantly worse with eye closure for sensory ataxia.
Sensory ataxia may be an indication of peripheral neuropathies and disorders causing dysfunction of the spinal cord’s posterior columns due to a number of various disorders.
Sensory ataxia is a result of a damage located either along the peripheral or central sensory nerve pathways. The peripheral sensory nerve pathways are located outside the spine and brain while the central sensory nerve pathways are located inside the spine and brain. One example of a damage to the peripheral sensory nerve pathway is peripheral neuropathy which affects large sensory fibers. Peripheral neuropathy is a general term coiled for any type of condition or disorder of nerves located outside the spinal cord or brain. Peripheral neuropathy is a lack of sensation or in some cases a tingling pain or a burning sensation that starts at the bottom of the feet, usually in the toes, and spreads gradually up to the legs symmetrically. This damage can make it hard to maintain balance and coordinate movements because human beings are very dependent on the information that is coming from the bottom of the feet to inform them where the ground is, and they are continuously making tiny adjustments in the toes, ankles, and feet to maintain the center of gravity.
Another source or origin of sensory ataxia is a damage to the posterior columns of the spinal cord, which plays a significant role in the position sense and sense of touch. The damage can be caused by a variety of disorders: auto-immune, hereditary, infectious, metabolic, vascular, and toxic diseases, and multiple sclerosis.
An individual affected by sensory ataxia has almost normal coordination when walking with eyes open because he/she can use his/her vision to navigate movements.
When the individual loses his/her eyes, however, and he/she can only depend on touch and position sense, coordination is much more challenging, in fact, worse in sensory ataxia.
Individuals with sensory ataxia have a hard time controlling their balance and are not aware where their limbs are when they close their eyes, are in the dark or in low light,
or when pulling their clothes over the head. Someone with sensory ataxia has a hard time dressing and undressing the upper body.
During a physical examination, an individual with sensory ataxia demonstrates a positive Romberg sign which means that there is an imbalance when the individual is standing with his/her eyes closed. The arms are usually held out and they tend to wander and shake during a positive Romberg test. Pseuduoathetosis, abnormal writhing movements that usually occur in the fingers resulting from a poor position sense, is also another sign of sensory ataxia. Fingers may move out of position but they are not likely to move in an uncontrolled and quick manner just like what can happen in cerebellar ataxia.
Sensory ataxia is defined by striking or stamping the ground hard on each step with the bottom of the foot and also a stiff fling of the leg which may sometimes be described as ‘walking on pillows’. This is a result of the loss of sensation in the legs and feet wherein the affected individual develop an unsteady stomping gait. This can also be associated with pain in the legs and feet.
When referred to a specialist, the doctor’s diagnosis of the condition is made based on an individual’s medical history, a physical examination, answers to questions about symptoms, and the result of tests. The tests can include a blood test and a nerve conduction study to determine how well the messages are being carried from areas such as the legs and feet up to the brain and spine.
Criteria for diagnosing sensory ataxia through clinical examination:
- Finger-nose incoordination
- Broad-based ataxic gait
- Heel-toe ataxia
- Romberg’s sign or ataxia is significantly worse when the eyes are closed
- Absence of nystagmus and/or cerebellar ataxia
- Pseudoathetosis and/or vibration senses and/or impaired joint position
A lot of cases of peripheral neuropathy can be diagnosed clinically but sometimes, nerve conduction studies are also required. An electrical current is applied to the nerve, stimulating the nerve, and measuring the response down the nerve. Electrical stimulation does not cause any damage to the nerve but there is typically a mild temporary discomfort that is experienced by an individual. There are certain blood tests that are required to look for the cause of neuropathy. The common causes of neuropathy are vitamin B-12 deficiency, diabetes, age-related, and alcohol-related.
A testing of vibratory sense may also be done on a suspected patient. The position sense and vibration sense are often lost together for an individual with sensory ataxia. Usually, one of them may be affected disproportionately. As the individual grows up, vibration is the sense that is most commonly lost especially at the ankles and at the toes.
Just like all the other forms and types of ataxia, there is currently no known cure for sensory ataxia. There are just treatments available to try to lessen or if not stop the progress of the damage on the nerves, ease the symptoms, minimize the risk of falls, and increase independence. If a cause is found for having sensory ataxia, treatment is immediately given to address the underlying cause.
An individual with sensory ataxia needs to work well with occupational therapists and physiotherapists to maintain as much independence as possible and for a guaranteed safety of mobility.
Treatment for the underlying conditions may include occupational therapy, physical therapy, nerve stimulation, or even medications.
Occupational therapy can help a patient make adjustments to their home and environment and also help a patient do daily living activities easier.
Balance physiotherapy, specialist, and the use of mobile devices may be essential and there are special medications that can be prescribed to control the pain of the nerve origin when necessary.
A patient with vitamin B-12 deficiency is treated with a supplementation of vitamin B12 which may either be through injections or through oral.
Maintaining tight sugar control is recommended for the patients with symptoms of a diabetic neuropathy.
Lifestyle adjustments such as using a nightlight or a flashlight can be very helpful when walking in the dark. The sense of vision can also help a lot when an individual is trying to navigate the environment.