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 and structures. Given this it is essential that rehabilitation professionals have the ability to recognise key elements of the objective assessment, which may be indicative of impairment to the nervous system, which could have the potential risk for serious adverse events.

The neurological screen is a “quick scan", can be performed rapidly with practice, to rule in or out symptoms that might suggest neurological involvement, which may be referred from one part of the body to another. The neurological screen has always been considered a key element of safe and appropriate practice, and is commonly used to assess the integrity of the nervous system and determine a patients neurological function. The presence of an abnormal result within the neurological screen will typically warrant further investigation and onward referrals to specific specialties. Even though neurological screening provides essential diagnostic information and have direct implications for management decisions, there is substantial variation in what is included in a neurological examination and how it is performed.

Purpose

Clinicians utilise a neurologic screen both as a differential diagnostic tool to help clinician's identify alterations in somatosensory and motor nerve functions that may rule in or out impairments to the nervous system, and as a tool to monitor for changes in symptoms with treatment. The main purpose of the neurological screen is to help the clinician to determine whether any impairment of the nervous system identified is caused by the central nervous system or peripheral nervous system and to localise the impairment to the specific structures e.g. nerve root, peripheral nerve.
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 or if a patient presents with any of the following:

• Injury to the Head or Spine
• Headaches
• Dizziness
• Seizures
• Blurry or Double Vision
• Loss of Smell
• Impaired Hearing
• Impaired Speech
• 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

Principles of Neurological Screening

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.

Even though neurological screening provides essential diagnostic information and have direct implications for management decisions, there is substantial variation in what is included in a neurological examination and how it is performed. The following assessments are key components of the neurological screen.

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. Deep-tendon, pathological and superficial reflexes all supply a wealth of information on localization and identification of upper and lower motor neuron lesions.

Reflexes are the body’s intrinsic stimulus-response systems for maintaining homeostasis, and are often used for diagnosing and localising nervous system disorders. When performed and interpreted correctly, reflex testing provides the examiner with some of the most object evidence that can be obtained in neurological testing. Reflexes may be divided into 4 groups:

1. Deep Tendon Reflexes
2. Superficial Reflexes
3. Pathological Reflexes
4. Visceral Reflexes

Pathological and superficial reflexes share a unique inverse relationship. Under normal circumstances, pathological reflexes are absent and superficial reflexes are present. Under abnormal circumstances (usually upper motor neuron pathology), pathological reflexes present and superficial reflexes disappear. Deep-tendon, pathological, superficial and visceral reflexes all supply a wealth of information on localisation and identification of upper and lower motor neuron lesions. The most common reflexes used during a neurology screen are deep tendon reflexes and superficial reflexes.

Table.1 Summary of Key Reflexes Used in Neurological Sreening

Type of Reflex	Reflex	Afferent Nerve	Centre	Efferent Nerve
Superficial Reflex	Plantar Reflex	Tibial	S1-2	Tibial
	Anal Reflex	Pudendal	S4-5	Pudendal
Deep Tendon Reflexes	Biceps Brachii	Musculocutaneous	C5-6	Musculocutaneous
	Brachioradialis	Radial	C5-6
	Triceps	Radial	C7-8	Radial
	Patellar	Femoral	L2-4	Femoral
	Achilles	Tibial	S1-2	Tibial

You can read more about the reflexes and reflex testing here

Deep Tendon Reflexes

Deep tendon reflexes, commonly referred to as the tendon jerk, are the most common reflex tested during a neurological screen. 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	Characteristic of Reflex	Suspected Lesion
0	Reflex Absent	Lower Motor Neuron
1	Somewhat Diminished or Requires Reinforcement	Lower Motor Neuron
2	Average	No Lesion
3	Brisker than Average	Upper Motor Lesion
4	Very Brisk with Clonus	Upper Motor Lesion

A better method of reflex interpretation is to use the patient to establish normal and judge by symmetry. Some people have very good reflex responses, while others have very poor reflex responses. If a person has good responses symmetrically, then that is probably normal for that person and likewise if a person has poor responses symmetrically, then that is probably normal for that person. Thus, the absence of reflexes is not necessarily pathological.

What is key is asymmetry. If a person has good responses in most muscles, but one muscle provides a decreased response, it is a sign of hyporeflexia. If a person has minimal responses in most muscles, but one muscle provides a greater response, it is a sign of hyperreflexia. Using the patient as their own baseline and symmetry are key factors in diagnosis using deep tendon reflexes.

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 peripheral 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 rehabilitation professionals can gain insights into potential neural abnormalities and must be able to differentiate between a dermatome (nerve root) from the sensory distribution of a peripheral nerve,

Read more about sensation and the sensory pathways here.

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.

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 dermatomes involves bilateral comparison of light touch discrimination and 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

Peripheral Nerves

Table. 1 Common Peripheral Nerves and their Nerve Root Derivation

Peripheral Nerve	Nerve Root Distribution
1st column 2nd row	2nd column 2nd row
1st column 3rd row	2nd column 3rd row
1st column 4th row	2nd column 4th row

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.

Peripheral Nerves

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

Clinical Significance

	Upper Motor Neuron	Lower Motor Neuron
Site of Lesion	Cerebral Hemisphere Cerebellum Brainstem Spinal Cord	Anterior Horn Cell Motor Nerve Roots Peripheral Motor Nerves
Observation	No Fasiculations No Significant Wasting	Fasiculation Atrophy
Tone	Increased Hypertonia Spasticity or Rigidity	Decreased or Normal Hypotonia Flaccid
Deep Tendon Reflexes	Exaggerated or Brisk Hyperreflexia	Reduced or Absent Hyporeflexia or Areflexia
	Babinski Positive - Upgoing	Babinski Negative - Downgoing
Sensation	Sensory Loss in Dermatomal Pattern	Sensory Loss in Peripheral Nerve Pater
Strength	Reduced - Pyramidal Pattern of Weakness Extensors weaker than Flexors in Upper Limbs Flexors weaker the Extensors in Lower Limbs	Reduced - Distribution of Affected Motor Nerve Root Peripheral Motor Nerve

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