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|Year : 2018 | Volume
| Issue : 5 | Page : 1381-1382
Accuracy and reliability of Babinski sign versus finger and foot tapping in the diagnosis of corticospinal tract lesions
Department of Neurosurgery, Madras Medical College, Chennai, Tamil Nadu, India
|Date of Web Publication||17-Sep-2018|
Dr. R Raghavendran
Department of Neurosurgery, Madras Medical College, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Raghavendran R. Accuracy and reliability of Babinski sign versus finger and foot tapping in the diagnosis of corticospinal tract lesions. Neurol India 2018;66:1381-2
|How to cite this URL:|
Raghavendran R. Accuracy and reliability of Babinski sign versus finger and foot tapping in the diagnosis of corticospinal tract lesions. Neurol India [serial online] 2018 [cited 2019 Aug 24];66:1381-2. Available from: http://www.neurologyindia.com/text.asp?2018/66/5/1381/241383
Diagnosing pyramidal tract lesions in the late stages is relatively easier. An early identification of corticospinal involvement to decide the management protocol, and especially in planning surgical intervention, has always been challenging.
The output of the cerebral hemispheres is predominantly motor and often presents as a pure motor syndrome. We usually become aware of the involvement of the pyramidal tract by observing the motor performance. Pyramidal tract involvement mainly affects the level of alertness, the ability to perform a task, and finally, the ability to carry out a sequence of movements, which is in essence the motor act itself. Loss of dexterity in movement is one of the most characteristic signs of corticospinal tract (CST) involvement. This loss of dexterity usually presents as a defect in the voluntary control of fine distal movements, which in simple terms is known as clumsiness, stiffness or slowness of movements. Pathological hyperreflexia and Babinski sign are crucial manifestations of upper motor neuron (UMN) involvement. They may be seen sometimes only in the later stage of the disease.
Clinical screening examination to identify an early involvement of the pyramidal tract is of paramount importance in any neurological examination. Diagnosing it in the early stages of involvement is a challenge. The clinical tests done separately often do not provide useful results. The examination done routinely is a combination of many clinical tests to identify the problem early; however, they only provide marginally better results. The standard tests have only moderate sensitivity even when performed by experienced clinicians and fail in adequately ruling out pyramidal tract involvement. We are in dire need of proper research-based assessment methods to define pragmatic, reliable, sensitive, specific, easy to perform and quick clinical methods for determining the presence or absence of CST involvement.
Repetitive rapid finger tapping test is invaluable in the early identification of the functional integrity of CST, cerebellar and proprioceptive pathways., Finger tapping is considered more complex and involves the performance of multidimensional tasks when compared to the foot tapping test, and this may be the reason for its high sensitivity and early occurrence in pyramidal tract involvement. It requires coordinated alternating activity of flexor and extensor group of muscles. Also, several scientific publications have concluded that finger and foot tapping have a high sensitivity as well as a high inter-evaluator reliability with a high kappa value on agreement and has consistent reproducibility.
Finger tapping abnormality of the non-dominant hand is more sensitive and specific than the findings on the dominant limb. This is due to the presence of lesser reserve capacity in the motor pathway controlling the non-dominant side. The dominant motor pathway is more efficient and has a greater functional capacity. This highlights the importance of identifying CST involvement at a very early stage by focusing on the less dexterous, non-dominant limb examination. Enhancing training to young neuro-scientists for developing neurological examination skills is required for enabling an early identification of CST impairment. Foot tapping and finger tapping, when combined, had a higher sensitivity as compared to the sensitivity in detecting CST involvement when either of the two tests was utilized alone.
Foot and finger tapping tests have the potential to be captured in a video movie. Also, the density of the longitudinal data is higher because of the measurability of the test on multiple occasions on the same day; and, its objective assessment even by the patients in domiciliary care is a very good screening method. Results of multiple evaluations can be averaged for more accuracy.
The clinical tests classically associated with pyramidal tract involvement and usually performed during a neurological examination are the Hoffman's sign, the poorly coordinated gait and stance, the presence of limb weakness, the exhibition of primitive reflexes, the finger escape sign, the grip release test, the exaggerated deep tendon reflexes, the inverted supinator jerk, the positive suprapatellar quadriceps test, as well as the presence of hand withdrawal reflex, the Babinski's sign and clonus. The clinical evaluation of a patient with pyramidal tract involvement is of paramount importance for the initiation of a proper management plan. Failure to accurately and efficiently quantify pyramidal tract involvement and also the failure to achieve an early identification of its impairment may result in progression of symptoms to an irreversible stage. The early identification of CST involvement particularly in spinal cord lesions is important since an early surgical intervention is beneficial in achieving a good outcome in these patients. The clinical findings for an early identification of impairment in the CST tract, which involve the usage of both the screening methods and the diagnostic tests, should have a good reliability, a high sensitivity, a high inter-observer agreement and an unambiguous diagnostic value.
Screening tests need to be inexpensive and relatively accurate. They should assist the clinician in ruling out selected diagnoses, with a high sensitivity during an early stage of the disease. They should have a low false negative prediction rate to avoid any mistake in identifying a patient as normal, when the patient is actually diseased. On the other hand, a false positive prediction rate is common in the presence of compressive myelopathy, as the extent of spinal cord compression as seen on radiological imaging often does not correlate with the clinical presentation.
The diagnostic value of the Babinski's sign and the inverted supinator reflex have been found to be strong, with a high specificity. The inherent sensitivity of these tests is not strong enough to acknowledge these tests as accurate screening tests for unequivocally establishing the presence of myelopathy. The crossed upgoing toe sign is more specific than the Babinski's sign. Even a combination of several tests do not provide a high sensitivity in order to rule out or identify CST involvement at an early stage. Babinski's sign may be absent in some cases of compressive myelopathy with lower extremity weakness and can lead to the misinterpretation of the final diagnosis.
Correlation of radiological features with clinical tests for establishing the diagnostic accuracy of the latter reveals that the most accurate sign that predicted myelomalacia changes as revealed on magnetic resonance imaging (MRI) of the spinal cord was the Babinski's sign. Babinski's sign alone had a higher specificity and sensitivity in predicting myelomalacia changes on MRI compared to a combination all the other tests routinely used to identify CST involvement. However, the presence of Babinski's sign is not an early finding, or in other words, not seen early in cases with less severe involvement of the pyramidal tract. The diagnostic accuracy of the inverted supinator reflex in predicting myelomalacia was second behind the Babinski's sign. On the other hand, the absence of an inverted supinator reflex had a high degree of diagnostic accuracy in predicting the absence of changes of myelomalacia, as seen on MRI. Several scientific studies have revealed consonant findings with the above mentioned conclusions.
The limbic motor system controls the emotional output and expression, with a strong influence over the motor neurons. This emotional experience and status of an individual can also significantly influence the overall spinal cord activity.
Most of the clinical tests have a good sensitivity in ruling out CST involvement but the negative findings often obtained while performing these tests may lull the clinician into a false sense of security. The risk of obtaining misleading results is fairly high. The compounding factors that increase the risk of obtaining erroneous results on neurological examination include the age of the patient, the presence of arthritic and degenerative changes in the joints, the duration of symptoms, and the functional status of the patient. Ambiguity can actually be amplified by the complexity of the disease and weakness of the test method employed. The need for a thorough neurological examination cannot be overemphasized when it comes to early identification of pyramidal tract lesions.
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