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 health 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", that 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 assessment to ensure safe practice, and is typically 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 may warrant further investigation and onward referrals to specific specialties.

Purpose

Clinicians utilise a neurologic screen both as a differential diagnostic tool to help identify altered somatosensory and motor nerve functions that may rule in or out impairments to the nervous system, and also as a tool to monitor changes to somatosensory and motor function with intervention.

The main purpose of the neurological screen is to help the clinician to determine whether any identified impairment of the nervous system is caused by the central nervous system or peripheral nervous system and localise the impairment to sensory upper or lower motor neurones.

• Sensory Neurones, which send signals back to the brain via the spinal cord;
• Upper Motor Neurones, which originate in the cerebral cortex and travel down to the brain stem or spinal cord; or
• Lower Motor Neurones, which begin in the spinal cord and go out 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 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
• Muscle Weakness
• Radicular Signs
• Numbness or Tingling in the Arms and/or Legs.
• Changes in Bowel and Bladder Function
• Presents with Abnormal Patterns
• Altered Mental State; confusion, memory loss, cognitive decline or reported changes in behaviour

Principles of Neurological Screening

When performing the neurological screen, it is important to always keep the purpose of the assessment in mind as you go through it, namely to localise the lesion to specific structures within the nervous system.

• Explain Process: Briefly explain to the patient that you are going to perform a series of tests that will help you determine where their symptoms might be coming from. Explain and demonstrate what you will be doing and show them any devices or equipment that will such as a reflex hammer. This is to ensure the patient understands what you are doing and can alleviate any fear or worry.

• Adequate Positioning: Adequately expose the area to be tested and drape the patient as required. Ensure the patient is comfortable, well supported and relaxed with the area being assessed positioned to allow for complete and unobstructed movement. Testing positions will vary depending on which element of the neurological screen you are completing. Consider your approach to minimise changes in position during the process.

• Procedural Skills: Ensure you have developed good procedural skills for each of the neurological assessments that form part of the screen including preparation and set up, safety, knowledge and decision making, communication and comfort and use a consistent approach to your assessment process to improve the reliability and validity.
• Interpret Findings: The results of the neurological screen are all weighed up together to identify the lesion, which may be highly specific (for example abnormal sensation in one dermatome) or diffuse such as in neuromuscular diseases. In interpreting your findings consider the following;
  • Symmetry: Observe side to side symmetry: typically one side of the body serves as a control for the other;
  • Determining whether your findings suggest peripheral nervous system, central nervous system involvement or both, considering also whether there is a single lesion or a multifocal process occurring.
  • Location: Establish the location of the lesion.

Even though neurological screening provides essential diagnostic information and can have direct implications for management decisions, there is often substantial variation in what is included in a neurological examination based on signs and symptoms identified during your assessment. The following assessments are key components of the neurological screen.

Reflex Assessment

A reflex is an automatic and nearly instantaneous involuntary movement of an organ or body part in response to a stimulus, that happens without any conscious thought as a result of a reflex arc. The reflex arc is a neural pathway that mediates or controls the reflex reaction of the body. Reflex arcs act on an impulse before that impulse reaches the brain.

Reflexes are the body’s intrinsic stimulus-response systems for maintaining homeostasis, and when performed and interpreted correctly are the most objective evidence within the neurological screen to localise the lesion to specific structures within the nervous system. Reflexes may be divided into 4 groups:

1. Superficial Reflexes; Elicited by stroking the skin or mucous membranes
2. Deep Tendon Reflexes; Elicited by a stretch stimulus applied to a muscle
3. Visceral Reflexes;
4. Pathological Reflexes; Reversions to primitive responses and indicate loss of cortical inhibition.

While all categories of reflex supply a wealth of information to localise impairment to specific structures within the nervous system, here we will focus on the most common reflexes used during a neurology screen, which are outlined below in more detail.

You can read more detail about reflexes and reflex testing here.

Superficial Reflexes

Superficial reflexes, also known as cutaneous reflexes, are usually elicited by stroking the skin or mucous membranes.

The following table highlights the most commonly used superficial reflexes in a neurological screen. (Table.1)

Table.1 Summary of Key Superficial Reflexes Used in Neurological Screening

Reflex	Nerve Supply	Segmental Innervation	Description of Action	Normal Reflex Response
Plantar Reflex	Tibial	S1-2	Stroke Sole of Foot	Plantar Flexion of Toes
Anal Reflex	Pudendal	S4-5	Stroke Perianal Area or Insert Gloved Finger into Rectum	Contraction Sphincter Ani

Deep Tendon Reflexes

Deep tendon reflexes, also known as the tendon jerk, are the most common reflex tested during a neurological screen. Deep tendon reflexes are stretch reflexes mediated through neuromuscular spindles within the muscle, which evaluate afferent nerves, synaptic connections within the spinal cord, motor nerves, and descending motor pathways. The testing of the muscle stretch reflex provides the clinician with a direct way of assessing the peripheral nervous system and an indirect way of examining the central nervous system to determine if whether an upper or lower motor neurone lesion is present.

Lower Motor Neurone Lesion = Decreased or Absent Reflex (Hypo-reflexia) due to reduced descending inhibition

Upper Motor Neurone Lesion = Increased Reflex (Hyper-reflexia) due to loss of inhibitory modulation of descending pathways

Unilateral absence implies impairment at the peripheral nerve or root level.

Absent response indicates a complete lesion somewhere along the neural pathway or in the muscle itself.

A reflex hammer is used 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 patient should be in a relaxed position with the muscle in a resting state. Clinician palpates the tendon to establish the point of contact for the reflex hammer. Holding the reflex hammer loosely allowing momentum to swing the hammer freely, the clinician strikes briskly over the tendon to place a slight quick-stretch to elicit a reflex response.

Figure.1 Jendrassick Manoeuver

Where the patient finds it difficult to relax during reflex testing you can also perform a jendrassik manoeuvre, which facilitates activity of the spinal cord, accentuating a minimally active reflex. These manoeuvres primarily increase the sensitivity of the muscle spindles and decrease inhibition of the central nervous system, which in turn heighten or exaggerate the reflex  and make it easier for the examiner to see the reflex. Examples of jendrassik manoeuvers include clenches teeth, pushes knees together, interlocking fingers and trying to pull them apart.

The following table highlights the most commonly used deep tendon reflexes in a neurological screen. (Table.2)

Table.2 Summary of Key Deep Tendon Reflexes Used in Neurological Screening

Reflex	Nerve Supply	Segmental Innervation	Description of Action	Normal Reflex Response
Biceps Brachii	Musculocutaneous	C5-6	Tap Biceps Tendon	Biceps Contraction
Brachioradialis	Radial	C5-6	Tap Brachioradialis Tendon or just Distal to Musculotendinous Junction	Elbow Flexion and/or Forearm Pronation
Triceps	Radial	C7-8	Tap Distal Triceps above Olecranon Process	Elbow Extension
Patellar	Femoral	L2-4	Tap Patellar Tendon	Leg Extension
Achilles	Tibial	S1-2	Tap Achilles Tendon	Plantarflexion

Grading of deep tendon reflexes uses a 5-point scale to characterise the stretch reflex response (Table.3). When interpreting reflexes the clinician should consider both what is normal for the patient and symmetry. Comparison between reflexes in one part of the body and another is much more important than the absolute reflex grade. The most important comparison is between corresponding reflexes on the right and left, where even subtle asymmetry may be significant. Many examiners may augment the scale by using + or - to designate intermediate grades.

Table.3 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

Pathological Reflexes

Primitive reflexes are considered typical in infants until integrated and then disappear. These primitive reflexes are pathological if found in adults, and outside of the realm of what is considered to be normal, and are indicative of an underlying problem with the nervous system. Pathologic reflexes are reversions to primitive responses and indicate loss of cortical inhibition. The most common pathological reflexes used during neurological screening are highlighted below, which all demonstrate upper motor neurone lesion (Table.4):

Table.4 Summary of Key Pathological Reflexes Used in Neurological Screening

Reflex	Pathology	Description of Action	Response
Hoffman's Sign	Pyramidal Tract Lesion	Flicking the distal phalanx of the index finger	Adduction and Opposition of the Thumb and Slight Flexion of the Fingers.
Babinski's Sign	Pyramidal Tract Lesion	Stroke plantar surface of foot from heel to great toe, starting from lateral side and sweeping across to medial side at ball of the foot.	Extension of Great Toe
Clonus Reflex	Pyramidal Tract Lesion	Forcibly and quickly dorsiflexing the foot while holding up the leg under the popliteal space.	More than three involuntary beats or continued rapid flexion and extension of the foot.

Sensory Assessment

Sensory assessment is a commonly utilised method for assessing the functionality of the nervous system without invading the body. It is largely a subjective examination that requires an alert, cooperative patient who can give reliable subjective impressions of various stimuli.

This approach relies on understanding the dermatomes and sensory regions of peripheral cutaneous nerve innervation. 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 a dermatomal pattern of sensory loss for each nerve. Clinicians should be able to differentiate between a dermatome (nerve root) from the sensory distribution of a peripheral nerve. Examination of cutaneous loss over dermatomes is necessary only when suggested by the history. Although a conclusive diagnosis cannot be reached exclusively through sensory testing alone, it remains an essential tool to help localise the impairment.

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.

Multiple definitions of dermatomes exist, and several maps are commonly employed. Typically two primary maps of dermatomes, Foerster Map (Figure.1) and the Keegan and Garret Map (Figure.2), are recognised and used within rehabilitation settings. Although they are valuable, dermatomes vary significantly between maps and even among individuals, with overlap between dermatomes commonly seen, with some evidence suggesting that current dermatome maps are inaccurate and based on flawed studies. There are less, if any, overlap between non-consecutive dermatomes, and therefore these boundaries can give more reliable and clinically useful borders. To maintain consistency in your approach to dermatome testing determine which dermatome map you are going to use, and consistently use this in all your testing and communicate this with other healthcare professionals.

The history will usually determine whether examination of dermatomes is required, with the patient asked to indicate any area of altered sensation, including its limits. The examination should focus on the region suggested by the history rather than assessment of every dermatome. Assessment of dermatomes involves bilateral sensory testing, which should follow a standard procedure. typically light touch has been used for sensory testing, but recent evidence suggests that circumferential pin-prick should be used for primary dermatome testing if peripheral neuropathy is suspected followed by thermal testing in the area of maximal of pain if pin-prick testing is normal, which allow evaluation of small fibre function.

• Move from distal to proximal along the long axes of limbs, and ascend vertically on both sides of the trunk.
  • Where there is a reported loss of sensation the assessment should start from the centre of the area of maximum abnormality and extend towards the normal area to define the borders of the area of altered sensation.
  • Where there is a reported area of enhanced sensation, typically hyperalgesia, the examination should proceed in the reverse direction, starting at the normal area and extend towards the area of increased sensation.
  • Bender et al suggest that you can better differentiate dermatome from peripheral innervation patterns using a circumferential pattern rather than just point testing as this covers most dermatomes and peripheral innervation territories, which can be viewed here for the lower limbs and upper limbs. They also suggest a star-shaped pattern to support delineation of sensory loss that can be viewed here.
• Patients confirm recognisable sensations whether that be light touch, sharp, temperature etc.

You can read more about dermatomes here

Motor Assessment

When performing the motor examination on a patient presenting with weakness, it is important to remember that this can result from a lesion at any point in the nervous system: cerebral hemispheres, brain stem, spinal cord, anterior horn cell, nerve root (myotome), peripheral nerves, neuromuscular junction, or muscle. Motor assessment typically involves manual myotome testing of reference muscles that are then further supplemented by functional assessment with identification of any muscular atrophy, although this alone will not typically differentiate between nerve root or distal nerve trunk compromise.

Myotomes

The term “myotome” is a combination of two Greek words; “myo” meaning “muscle”, and “tome”, meaning “cutting” or “thin segment”. Myotomes represent a group of muscles that are innervated from a single specific nerve root. Essentially, myotomes are the motor equivalent to dermatomes. Myotome testing is performed using manual muscle testing, through sustained isometric contraction of the specific group of muscles. Table.3 below details which movements have the strongest association with each myotome.

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	Ana l Wink
T1	Finger Abduction

Bender et al recommend that further testing should be completed if weakness identified on myotome testing to establish if this weakness is consistent with nerve root or distal nerve trunk compromise. For example, a weakness of the extensor pollicis longus could be caused by a C8 nerve root or radial nerve lesion. To assist the clinical reasoning process is test a radial nerve muscle that is not innervated by C8 nerve root (eg, brachioradialis) followed by testing a muscle innervated by C8 nerve root but not radial nerve (eg, abductor digiti minimi).

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:

• Results of each test must be interpreted in the context of other findings.
• Consider side to side symmetry: one side of the body serves as a control for the other.
• Determining whether impairment involves the peripheral nervous system, central nervous system or both.
• Establish the location of the impairment.
• Carefully measure neurological deficits to ensure you are objectively monitoring changes over time.

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

References