Lower limb neurological examination

Acronym

Is That Position Really So Cool?

Introduction

Introduce yourself, confirm the patient's name and date of birth, obtain consent and proceed to wash hands.

General inspection

Begin the examination by asking the patient to lie comfortably on the bed. The bed should be no more than 30o. It is important to briefly assess the general appearance of the whole body, and that includes the upper limbs and face. Ensure that the patient is exposed from the waist downwards such that the entire lower limb can be seen.

Ask the patient about pain and comfort. Pain can indicate acute injury or be secondary to pathology. However, we primarily ask about pain to avoid hurting the patient and maximise their comfort. Next, look for paraphernalia around the bed. It is important to look out for walking aids, blood glucose monitors and medication.

Closer inspection

Look for any scarring, rashes, muscle wasting, fasciculation or dyskinesia. Wasting and fasciculation can be due to a lower motor neurone (LMN) lesion, and it is most notable usually at the quadriceps femoris and anterior tibialis. Dyskinesia (involuntary movements) can be caused by a variety of pathologies including Huntington's disease.

Look at the shape, size, and general condition of the foot. Look for deformities such as hammer toe (a permanently bent toe at the proximal interphalangeal joint), flat foot or pes cavus (high arched foot). Charcot-Marie-Tooth disease can result in Charcot foot, in which there will be several mechanical and vascular features resulting in foot deformity.

Also keep an eye out for neuropathic, arterial or venous ulcers. The presentation of these is usually as follows:

Some students use the mnemonic DWARFS to help remember what to look for in closer inspection. Dyskinesia, wasting, asymmetry, rashes, fasciculation, scars.

Tone

To assess tone, assess the muscle groups at the hip, knee and ankle joints, comparing each side like for like. Ensure the patient is relaxed, place your hands on their knee and roll the leg such that there is rotation at the hip. Repeat with the other leg. Lift each knee briskly at least 30cm off the bed and then release - the knee should drop and the leg straighten. If the foot also comes off the bed with the knee, then this indicates hypertonia.

Circumduce the ankle joints. Circumduction assess all of the possible movements at this joint: flexion, extension, abduction, adduction and rotation.

Finish by testing for clonus by holding the sole of the patient's foot, quickly dorsiflexing the ankle, and holding it firmly flexed in that position. If there are greater than 5 involuntary contractions (beats) of the gastrocnemius muscle, then that may be a sign of an upper motor neurone lesion.

Hypotonia: This is usually due to a LMN lesion. Decreased tone is difficult to detect, so caution on presenting.
Hypertonia: Hypertonia, or spasticity, can be described in different ways:

Power

Hip: Ask the patient to raise one of their legs whilst keeping the knee extended. Test flexion (L2-3, femoral nerve) and extension (L4-5, inferior gluteal nerve and sciatic nerve) at the hip joint by applying a downwards and upwards force, while asking the patient to resist. Do the same with the other leg.

Knee: Flex the patient's knee to a 90o angle whilst keeping the foot flat on the bed. Test extension (L3-4, femoral nerve) and flexion (L5,S1, sciatic nerve) by asking the patient to kick out and pull their leg in, against resistance.

Ankle: Test ankle dorsiflexion (L4-5, deep peroneal nerve) and plantar flexion (S1,2, tibial nerve) by asking the patient to resist an upward and downward movement.

IMPORTANT: It is imperative that during assessment of power you isolate the joints. For example, when assessing extension at the knee, be sure to push on the patient's hamstrings to prevent any hip extension.
Additionally, you should be comparing power on each side, like for like.
There is no need to isolate the hip joint, as that is achieved through the positioning of the patient.

Power can be graded using the Medical Research Council (MRC) scale as follows:

  1. 0 - No contraction.
  2. 1 - Trace of contraction (fasciculation).
  3. 2 - Active movement with gravity eliminated.
  4. 3 - Active movement against gravity.
  5. 4 - Active movement against gravity and resistance.
  6. 5 - Normal power.


Decreased power indicates muscle weakness. It is important to identify the pattern of distribution. Weakness at one muscle group could indicate a mononeuropathy. Symmetrical and proximal weakness could be a result of myopathy. If the extensors are weaker than flexors, then there may be hemiparesis. In reporting, focus on the movement affected and the grade of power.

Reflexes

Show the patient the tendon hammer and orange stick, and proceed to test reflexes. There are three reflexes to elicit.

Hyporeflexia: This is usually due to an LMN lesion. The reflex arc involves LMNs in both the afferent and efferent pathways. Hence, if there is a lesion to the LMNs involved in the reflex arc, there will be hyporeflexia.

Hyperreflexia: This is usually due to an upper motor neurone (UMN) lesion. Whilst UMNs are not directly involved in the reflex arc, they exert an inhibitory effect which dampens the reflex response. If there is any lesion to an UMN corresponding to a reflex arc, then this may lead to hyperreflexia.



This is a special term used for when the toes dorsiflex on eliciting the plantar reflex. It is a sign of an upper motor neurone lesion.

Sensation

Sensation should be assessed in the distribution of the dermatomes. A dermatome is an area of skin which is supplied by a single spinal nerve root. Below are listed the areas of skin which are supplied by a single dermatome only.

Areas of skin with a single dermatome only on the lower limbs.

There are five parts to sensation, and they include response to fine touch, pain, temperature change, vibration and joint position. Direct the patient extend their legs such that they are in the anatomical position, as this will make it easy to assess sensation at each dermatome. It is also important that you ask the patient to close their eyes before assessing any sensation modality.

Dorsal columns-medial lemniscus pathway: Light touch, vibration sense and proprioception in the lower limb are communicated to the midbrain via the gracile fasciculus of the dorsal columns in the spinal cord. Information then travels via the medial lemniscus to the contralateral thalamus before communicating with the primary somatosensory cortex.

Spinothalamic tract: Light touch, pain and temperature sensation are communicated directly to the thalamus via the contralateral spinothalamic tract of the spinal cord.

Light touch is in fact the least useful modality to assess sensation with because whilst it is mainly communicated to the brain by the dorsal columns-medial lemniscus pathway there is also communication in the spinothalamic tract.



If there is loss of sensation at a particular dermatome, this suggests injury to the spinal root, as a dermatome is a patch of skin supplied by a single spinal root.



If there is a loss of sensation in a non-dermatomal distribution, this indicates injury to the peripheral nerves, causing a peripheral neuropathy.

Coordination

Place your palms just below the patient's feet and ask them to tap your palms with their left foot only, right foot only, both feet together and then both feet interchangeably. Inability to do this with ease suggests dysdiadochokinesia, a phenomenon indicative of cerebellar pathology.

Ask the patient to place their right heel on their left knee whilst you place your hand half a metre above their left foot. Next, instruct them to move their right heel down to their left ankle, and then lift their foot in the air such that their toes touch your hand. Then ask the patient to repeat this motion. After about 5 seconds of continuous movement ask them to do the same using the left heel instead. This exercise tests for dysmetria, a phenomenon also indicative of cerebellar pathology.

Dysdiadochokinesia is a term for the inability to perform rapid alternating movements. It is a feature of cerebellar ataxia.
Dysmetria is a term for a lack of coordination movement when there is purposeful movement, that is to say, when there is undershoot or overshoot when trying to reach a certain position. Dysmetria is also a feature of cerebellar ataxia

Romberg's test

Ask the patient to stand upright with their feet together and arms by their side. Ask them to maintain this position while they close their eyes. If there is a loss of balance at this point then the patient tests "positive" for Romberg's sign, and they have a loss of vestibular function or proprioception.

It is important that at all times you are standing by the patient ready to catch them if they begin to fall. If the patient has a cortical or cerebellar lesion, then they may fall even when just getting off the bed.

Romberg's test is performed on the premise that the body requires at least two out of the following three senses to be functioning adequately to maintain balance while standing: vision, vestibular function and proprioception. If the patient can stand with their eyes open, then it can be said that vision and either one of vestibular function or proprioception are intact. Once the eyes are closed, then the patient is purely reliant on the latter two senses to maintain balance, and so if they fall, then this indicates that there is a problem with vestibular function, proprioception or otherwise the dorsal columns which communicate proprioception.



Romberg's test cannot be performed if the patient has a cerebellar lesion, as in that case, they will be unable to stand upright in the Romberg position with their eyes open. It is important to not confuse cerebellar ataxia with a positive Romberg's test, as the latter cannot even be performed in the presence of the former.

Gait

Following a negative Romberg's test, ask the patient to walk for 5m and check for any abnormalities in gait. These are described in the Complex Box below.

If the patient appears to have a normal gait, ask them to walk back to you heel-to-toe. This is more sensitive in picking up cerebellar ataxia.

Completion

Complete the examination by offering to obtain a full history, perform an upper limb and cranial nerve examination and then, if appropriate, suggest further tests such as nerve conduction studies (if nerve damage is suspected), a CT scan (if a recent stroke is suspected) or an MRI scan (if a demyelinating disorder or spinal lesion is suspected).

Interactive markscheme


When assessing each other, please click on each list item as you go along. Doing so will turn the list item green. Make careful note of any steps missed at the end.
We recommend completing any examination or procedure in under 10 minutes, but you can adjust the timer to suit your needs.
:

  1. Introduction: “Hello, I’m SimpleOSCE and I am a medical student. I need to examine and test the nerves in your legs today, would that be okay? Can I confirm your name and DOB? Thank you.”
  2. Wash hands.
  3. Position the bed flat and ensure adequate exposure.
  4. Ask about pain or discomfort.
  5. General inspection of the face, upper limbs and around the bed (walking aids, medication).
  6. Closer inspection of the lower limbs for scarring, rashes, wasting, fasciculation, dyskinesia or tremor.
  7. Check tone at the hip, knee and ankle joints.
  8. Ensure patient is relaxed and then test for clonus.
  9. Check power at the hip, knee and ankle joints.
  10. Ask the patient to relax and elicit the patellar and calcaneal reflexes. Attempt to do this twice per muscle only.
  11. Test for the plantar reflex using an orange stick.
  12. Check light touch sensation at all dermatomes with cotton wool (dorsal columns/spinothalamic).
  13. Demonstrate sensation first on sternum and ensure patient's eyes are closed throughout.
  14. Offer to check pain with neurotip (spinothalamic).
  15. Offer to check temperature with hot and cold test tubes (spinothalamic).
  16. Test proprioception by moving the big toe at the interphalangeal (IP) joint (dorsal column).
  17. Test vibration sense using the 128Hz tuning fork at the IP joint of the big toe (dorsal column).
  18. Test for dysmetria through "heel sliding" exercise.
  19. Test for dysdiadochokinesia through "foot tapping" exercise.
  20. Ask patient to stand with feet together to test for ataxia. Be ready to support patient if they fall.
  21. Perform Romberg's test ("close your eyes").
  22. Assess the patient's gait by walking and heel-to-toe.
  23. Thank and cover up the patient.
  24. "To complete my exam, I would like to take a full history and perform an upper limb neurological examination as well as a cranial nerve examination."
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