Neurological Screen

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Original Editors - Naomi O'Reilly

Top Contributors - Naomi O'Reilly and Jess Bell      

Introduction

Many rehabilitation professionals worldwide now assume a first contact role, which means that they may be the first medical professional to assess a patient presenting with impairments in body function. Given this it is essential that rehabilitation professionals have the ability to recognise the key elements of the patient subjective history, and the objective physical examination, which may be indicative of any serious pathology or a potential risk of serious adverse events. The neurological screening examination is a “quick scan" used to rule out symptoms, which may be referred from one part of the body to another and to assess the integrity of the nervous system.

The neurological screen has always been considered a key element of safe and appropriate practice, and is commonly used to determine a patients neurological function. A basic neurologic screen can be performed rapidly with practice, although there is no specific consensus of what to include or the order in which to perform the screen. The presence of an abnormal result usually warrants further investigation and onward referrals to specific specialties.

Why

Clinicians utilise a neurologic screen as a differential diagnostic tool to rule in or out such things as neurological diseases or injuries to the nervous system, and help clinician's identify alterations in somatosensory and motor nerve functions, which directly impact treatment plans but often do not use to their full potential for monitoring progress or deterioration. Clinicians can also determine whether signs and symptoms or alterations in function are caused by tissues innervated by the central nervous system or peripheral nervous system.

The main purpose of a neurological screen is to localise where in the nervous system the problem to one of the following areas;

• Upper Motor Neurones, which originate in the cerebral cortex and travel down to the brain stem or spinal cord;
• Lower Motor Neurones, which begin in the spinal cord and go on to innervate muscles.

To refresh your knowledge of neuroanatomy read here and to review your understanding of motor neurones read here.

Indications

A neurological screen is most appropriate to do when red flags are present. In cases where a patient sustained a possible injury to their brain, spinal cord or peripheral nervous system or if you feel one is appropriate.You may want to perform one as well, if a patient presents with any of the following:

• Injury to the Head or Spine
• Headaches
• Blurry or Double Vision
• Loss of Smell
• Impaired Hearing
• Impaired Speech
• Dizziness
• Seizures
• Tremors
• Change in Balance
• Change in Coordination
• Changes in Sensation
• Radicular Signs
• Muscle Weakness
• Numbness or Tingling in the Arms and/or Legs.
• Changes in Bowel and Bladder Function
• Presents with Abnormal Patterns
• Altered Mental State such as confusion, memory loss, cognitive decline or reported changes in behaviour

When performing the neurological screen, it is important to keep the purpose of the examination in mind, namely to localise the lesion to the nervous system.

Reflex Testing

A reflex is an involuntary and nearly instantaneous movement in response to a stimulus. The reflex is an automatic response to a stimulus that does not receive or need conscious thought as it occurs through a reflex arc. Reflex arcs act on an impulse before that impulse reaches the brain.

Several types of reflexes, including deep tendon reflexes, superficial reflexes, and pathological reflexes, can be tested as part of a physical examination and these all reveal something about the status of the elements of the nervous system that contribute to their functioning.

Deep Tendon Reflexes

Deep tendon reflexes evaluate afferent nerves, synaptic connections within the spinal cord, motor nerves, and descending motor pathways. Lower motor neuron lesions (eg affecting the anterior horn cell, spinal root or peripheral nerve) depress reflexes, while upper motor neuron lesions increase the reflexes.

Testing for deep tendon reflexes is most commonly used during a neurological screen using a reflex hammer to assesses the integrity of the stretch reflex arc of a specific nerve root, which provides information on the integrity of the specific nerve root. The rehabilitation professional strikes over the tendon insertion to place a slight quick– stretch on the tendon, which will elicit a reflex response (for example a muscle jerk response). The most common deep tendon reflexes assessed in the upper and lower extremities include the biceps, brachioradialis, triceps, patellar and the achilles tendon.

Table.1 Deep Tendon Reflexes

Segmental Innervation	Nerve Supply	Muscle
C5-6	Musculocutaneous	Biceps Brachii
C5-6	Radial	Brachioradialis
C7-8	Radial	Triceps
L2-4	Femoral	Patellar
S1-2	Tibial	Achilles

Grading of deep tendon reflexes uses a 5-point scale to characterise the stretch reflex response and compare it bilaterally to the uninjured limb.

Table.2 Deep Tendon Reflex Grading Scales

Grade	Description
0	Reflex Absent
1	Somewhat Diminished or Requires Reinforcement
2	Average
3	Brisker than Average
4	Very Brisk with Clonus

You can read more about the reflex arc and reflex testing here

Sensory Testing

Sensory testing is a commonly utilised method for assessing the functionality of the nervous system without invading the body. This approach relies on understanding the dermatomes and sensory regions of cutaneous nerves. Although a conclusive diagnosis cannot be reached exclusively through sensory testing, it remains an essential tool for pinpointing the origin of neural injuries. The peripheral nerves convey all skin sensations via their cutaneous branches as they extend into the trunk, while each spinal nerve supplies a specific area of skin, resulting in dermatomal patterns for each nerve. By examining these areas, healthcare professionals can gain insights into potential neural abnormalities.

Peripheral Nerves

Dermatomes

The term “dermatome” is a combination of two Greek words; “derma” meaning “skin”, and “tome”, meaning “cutting” or “thin segment”. Dermatomes are areas of the skin whose sensory distribution is innervated by the afferent nerve fibres from the dorsal root of a specific nerve root. Assessment of dermatomes involves bilateral comparison of light touch discrimination.

The idea of dermatomes originated from initial efforts to associate anatomy with the physiology of sensation. Multiple definitions of dermatomes exist, and several maps are commonly employed. Although they are valuable, dermatomes vary significantly between maps and even among individuals, with some evidence suggesting that current dermatome maps are inaccurate and based on flawed studies.

The medical profession typically had recognised two primary maps of dermatomes. Firstly, the Keegan and Garret Map (Fig.1) from 1948, which illustrates dermatomes in alignment with the developmental progression of the limb segments. Secondly, the Foerster Map from 1933, which portrays the medial area of the upper limb as being innervated by T1-T3, depicting the pain distribution from angina or myocardial infarction. This latter map is the most frequently implemented and is included in the assessment of spinal cord injury using the ASIA Scale. In recent years there have been few attempts at verifying these original dermatome maps. Lee et al conducted an in-depth review that examined the discrepancies among dermatome maps. They put forth an “evidence-based” dermatome map that combined elements of previous maps (Fig.3). Though the application of the term “evidence-based” may be somewhat questionable, their proposed map represents a systematic attempt to synthesise the most credible evidence available.

The history will usually determine whether examination of dermatomal sensation is required, with the patient asked to indicate any area of altered sensation, including its limits. Typically the examination focus on the region suggested by the history rather than assessment of every dermatome. Assessment of dermtomes should follow a standard procedure.

• Starting at the extremities, moving along the long axes of limb edges, and then upward on both sides of the torso helps ensure comprehensive examination.
• With noted sensory irregularities, the procedure commences at the core of the most affected zone and extends toward normal ranges to define abnormal perimeters.
• Conversely, in cases of heightened sensitivity, examiners begin closer to normal ranges and work towards greater sensory anomalies.
• Patients confirm recognisable sensations as "sharp" in each dermatome.
• Thermoreceptors are sometimes disregarded when standard pain responses seem typical.

You can read more about dermatomes here

Strength Testing

When performing the motor examination on a patient presenting with weakness, it is important to remember that weakness could be a result of a lesion at any point in the nervous system: cerebral hemispheres, brain stem, spinal cord, anterior horn cell, nerve root (myotome), peripheral nerve, neuromuscular junction, or muscle.

Myotomes

Myotomes represent a group of muscles that are innervated from a single specific nerve root. Essentially, myotomes are the motor equivalent to dermatomes. Myotomes may be assessed for various muscle groups of the upper and lower extremities. Myotome testing is performed through sustained isometric contraction of a specific muscle. Common muscles tested during myotome assessment are listed below.

Table. 3 Myotomes

Nerve Root	Upper Limb Movement	Nerve Root	Lower Limb Movement
C2	Neck Flexion	L2	Hip Flexion
C3	Neck Extension	L3	Knee Extension
C4	Neck Lateral Flexion	L4	Ankle Dorsiflexion
C5	Shoulder Abduction	L5	Big Toe Extension
C6	Elbow Flexion	S1	Ankle Plantarflexion
C7	Elbow Extension	S2	Knee Flexion
C8	Thumb Extension	S3-4	Anal Wink
T1	Finger Abduction

Summary

These are the main elements that should be considered when conducting a basic neurological screen. These tests reflect the function of various parts of the central and peripheral nervous system, and if assessed in a systematic and logical fashion can provide us with information on the integrity of the nervous system and an indication to what area of the nervous system is impaired.

The results of the neurological screen are taken together to anatomically identify the lesion, which may be diffuse (e.g., neuromuscular diseases) or highly specific (e.g., abnormal sensation in one dermatome due to compression or injury of a specific spinal nerve). When performing your assessment, please remember the following:

• Looking for side to side symmetry: one side of the body serves as a control for the other.
• Determining whether it  involves the peripheral nervous system, central nervous system or both.
• Establishing the location of the impairment.

We do not necessarily have to conduct every one of these assessments. Consider your patient’s history, including mechanism of injury, signs and symptoms and clinical reasoning in deciding when and what to assess.

References