Tandem gait is a component of certain neurological examinations and is most commonly used to assess cerebellar ataxia. The test dates back to the early nineteenth century. During the examination, patients walk in a straight line in heel-to-toe formation without support and whilst looking upwards. The test consists of at least ten steps. If a patient makes two or more missteps sideways across multiple trials of the test, they are considered to have an abnormal tandem gait. An abnormal tandem gait is most commonly a symptom of a cerebellar disease, but can also be observed in those with Huntington's disease, essential tremors, atypical parkinsonism, peripheral neuropathies, and vestibulopathies. A person with an abnormal tandem gait does not necessarily have ataxia, as there can be additional causes such as muscle weakness or visual impairments.
Definition Tandem gait is a component of the neurologic examination used to assess an individual's overall balance. In order to perform the tandem gait test, the patient walks in a straight line with their eyes open, placing the heel of the leading foot directly in front of the toes of the following foot so that the heel and toes touch, while keeping their arms at their side. This walk test is performed without any support. In order to supplement sufficient data for the physical examination, one must walk at least ten consecutive steps maintaining such form. This can be performed on any surface. In addition to medical diagnostic applications, tandem gait is used by police as a field sobriety test to detect impairment by alcohol or other drugs.
History Although explicit testing of the tandem gait as part of the neurological exam was not performed until the late 20th century, there are mentions of impaired balance and gait abnormalities secondary to cerebellar lesions in medical literature as early as the 19th century. Margolesky et al. (2018) note the first study that described impaired balance after cerebellar lesion was Luigi Rolando's Saggio sopra la vera struttura del cervello dell’uomo e degli animali e sopra le funzioni del sistema nervoso completed in 1809. The study found that after the medial lobe of the cerebellum in goats was partially resected, they had difficulty walking straight, swaying side-to-side and causing an increased number of falls. In 1824, Marie Jean-Pierre Flourens's Recherches experimentales sur les proprieties et les fonctions du systeme nerveux dans les animaux vertebres also found a similar gait disturbance in guinea pigs and dogs after cerebellar lesions. Additional studies performed by William Alexander Hammond and William Richard Gowers observed staggering or "drunken" gait in humans, noting the particular involvement of the middle cerebellar lobe and vermis in A Treatise on the Diseases of the Nervous System (1871) and A Manual of Diseases of the Nervous System (1888). In 1898, Charles Karsner Mills also mentioned lesions of the anterior and caudal cerebellar vermis in humans causing loss of balance with increased forward and backward falls, respectively, in The Nervous System and Its Diseases. In the early 20th century, as understanding of the nervous system and its pathologies increased, medical literature was published supporting the observation of abnormal tandem gait secondary to cerebellar vermal lesions. Examples of such literature include Nervous and Mental Diseases (1911) by Church and Peterson and Diseases of the Nervous System: A Textbook of Neurology and Psychiatry (1929) by Jelliffe and White. In 1998, Bastian et al. understood that each region of the cerebellum contributes to balance and posture in different ways, and that therefore a lesion in each region results in a specific balance impairment. They described the posterior vermal split syndrome in which the surgical resection of the posterior vermis in five children caused isolated impaired tandem gait. Patients were seen to be significantly swaying while attempting to tandem walk with frequent falls. In these same patients, there was minimal impact on Romberg stance, self-paced gait, one-legged stance, hopping, pinching, reaching, and kicking.
Pathologies of an abnormal tandem gait Two or more steps sideways out of the straight line that can be reproduced at least twice while walking heel-to-toe are considered an abnormal tandem gait. This most commonly signifies cerebellar disease but can also be seen in Huntington's disease, essential tremor, atypical parkinsonism, peripheral neuropathies, and vestibulopathies.
Cerebellar disease
The cerebellum is responsible for coordinated movements. The medial cerebellum is thought to have control over coordination of the body's truncal and limb girdle muscle movements specifically. Dysfunction or disease of the cerebellum causes ataxia. Disruption of gait, balance, or posture is commonly seen in cerebellar disease along with dysmetria, dysdiadochokinesia, speech changes, tremor, nystagmus, etc. Tandem walk is a test that can be used by physicians to test cerebellar control of gait/balance/posture. Those with disease of the middle cerebellum or vermis are likely to show an impaired tandem walk as well. Physicians use the term "ataxic gait" to describe those who have uncoordinated walking and difficulties with balance. The Scale for the assessment and rating for ataxia (SARA) is a tool to evaluate patients for signs of ataxia. It includes the tandem walk test asking patients to walk without support for at least 10 steps with heel-to-toe, forgiving only one misstep.
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