In this video, the examiner is testing the tone of the lower limbs. After ensuring that the patient is fully relaxed, he first of all rolls each leg using both hands – one placed above the knee and another below the knee. Then, the examiner lifts up each leg at the level of the popliteal fossa. Besides feeling for the tone, which is defined as the resistance to passive movement when voluntary contraction is absent, there are a number of features of hypertonia which can be observed in the video. First of all, when the examiner rolls the leg, there is a reduced swinging of the foot compared to patients with normal tone. Secondly, when the examiner lifts up the leg at the level of the popliteal fossa, the heel of the foot can be seen to be elevated from the surface of the bed, again indicating an increased tone. This patient had a history of transverse myelitis, and one can appreciate that the tone is increased over both legs.
Archive for the ‘Upper Motor Neuron Signs’ Category
Hypertonia
Wednesday, August 20th, 2014Up-going Plantar Reflex
Wednesday, August 20th, 2014To elicit this sign, the examiner strikes the patient’s sole using a blunt orange stick, starting from the heel, along the lateral border of the sole then medially to the base of the first toe. As one can see from the two videos, the patient demonstrates dorsiflexion of the big toe when testing for the sign. In some patients, there may also be fanning of the toes which is not very obvious in these two cases. Sometimes, the sign can also be elicited by striking other areas of the lower limb, such as the tibia and the ankle. The patient in the first video had a severe right cortical infarct resulting in left-sided upper motor neuron signs, whilst the patient in the second video had a history of transverse myelitis due to neuromyelitis optica resulting in upper motor neuron signs of both lower limbs.
Discussion of the sign
Up-going plantar reflex, or a positive Babinski’s sign, is considered a ‘hard’ neurological sign, which are signs that are objective and difficult to mimic. It is an upper motor neuron sign and any lesion along the cortico-spinal tract from the motor cortex to the spinal cord may result in this phenomenon. It has been proposed that loss of upper motor neuron control to local spinal circuits reproduces this primitive plantar reflex. It may be physiological in children before 1 year of age, but is otherwise pathological in older individuals, where the normal plantar response is downgoing. Of note, is that the foot should be fixed when eliciting the sign to minimise a withdrawal response, and the first direction of toe movement should be noted.
Also, as eliciting the sign often causes discomfort to the patient, it is preferable to use the blunt end of an orange stick when examining for the sign. Use of sharp objects (e.g. keys, pens or the sharp end of a tendon hammer) is discouraged. It is also of courtesy to warn the patient, whenever possible, that there will be some discomfort whilst testing for the sign.
Clonus
Wednesday, August 20th, 2014In this video, the presence of ankle clonus is being tested. Clonus is defined as a series of rhythmic, involuntary muscular contractions induced by sudden passive stretching of a muscle or tendon. To test for ankle clonus, the leg and foot should be relaxed and the knee and ankle placed in a slight flexed position. With one hand, the examiner stabilizes the lower leg and holds the foot with the other. The examiner then quickly dorsiflexes the foot whilst maintaining slight pressure on the sole. Unsustained clonus fades away after a few beats and may occur in normal individuals. Sustained clonus, as in this case, is when clonus persists as long as the examiner continues to exert slight dorsiflexion pressure on the foot. Sustained clonus is always pathological and is an upper motor neuron sign.