Neurological Screen

Original Editors - Naomi O'Reilly and Matt Huey

Top Contributors - Naomi O'Reilly and Jess Bell      

Introduction

Many rehabilitation professionals around the world now assume a first contact role. This means they may be the first health professional to assess a patient presenting with impairments in body function and structures. It is, therefore, essential that rehabilitation professionals recognise elements of the subjective and objective assessment that may indicate serious pathology, impairment to the nervous system or any other "potential risk of serious adverse events".

The neurological screen is a “quick scan" that, with practice, can be performed rapidly to rule in or out symptoms that might suggest neurological involvement. These symptoms may be referred from one part of the body to another. The neurological screen has always been considered an important element of assessment to ensure safe practice. It is typically used to assess the integrity of the nervous system and determine a patient's neurological function. An abnormal result in a neurological screen may require further investigation and onward referrals to specific specialities.

Purpose

Clinicians utilise a neurologic screen as a differential diagnostic tool to help identify altered somatosensory and motor nerve functions that may rule in or out impairments of the nervous system and 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 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: Send signals back to the brain via the spinal cord
• Upper Motor Neurones: Originate in the cerebral cortex and travel down to the brain stem or spinal cord
• Lower Motor Neurones: Begin in the spinal cord and go out to innervate muscles

To refresh your knowledge of neuroanatomy, see Introduction to Neuroanatomy. To review your understanding of motor neurones, see Motor Neurone.

Indications

A neurological screen is most appropriate 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 keep the purpose of the assessment in mind as you go through it (i.e to localise the lesion to specific structures within the nervous system).

• Explain Process: Briefly explain to the patient that you will perform a series of tests to 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 you will use, such as a reflex hammer. This ensures 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. The area being assessed must be 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 neurological assessment that forms part of the screen, including preparation and set up, safety, knowledge and decision making, communication and comfort. Use a consistent approach in your assessment 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 (e.g., abnormal sensation in one dermatome) or diffuse, such as in neuromuscular diseases. When 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.
  • determine whether your findings suggest peripheral nervous system, central nervous system involvement or both. Consider also whether there is a single lesion or a multifocal process is 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 sections discuss 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. This movement happens without conscious thought due to the reflex arc. A 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 test within the neurological screen to localise the lesion to specific structures within the nervous system. Reflexes may be divided into four 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: Reflexes that are initiated in the viscera and mediated by autonomic nerves
4. Pathological Reflexes: Reversion to primitive responses, which indicates a loss of cortical inhibition

While all categories of reflexes supply a wealth of information to localise impairment to specific structures within the nervous system, this page focuses on the most common reflexes used during a neurology screen.

To read more detail about reflexes and reflex testing, see Reflexes.

Superficial Reflexes

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

Table 1 highlights the most commonly used superficial reflexes in a neurological screen.

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. Testing 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 an upper or lower motor neurone lesion is present.

Lower Motor Neurone Lesion = decreased or absent reflex (hyporeflexia) due to damage to the alpha motor neurons that cause muscle contraction

Upper motor neurone lesion = increased reflex (hyperreflexia) due to reduced descending inhibition

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

Testing Procedure:

• A reflex hammer is used to assess the integrity of the stretch reflex arc of a specific nerve root.
• The patient should be in a relaxed position with the muscle in a resting state.
• The clinician palpates the tendon to establish the point of contact for the reflex hammer.
• Holding the reflex hammer loosely and allowing momentum to swing the hammer freely, the clinician strikes briskly over the tendon. This places a slight quick stretch and should elicit a reflex response.

Figure.1 Jendrassick Manoeuver

If the patient finds it difficult to relax during reflex testing, you can also perform a jendrassik manoeuvre (see Figure 1). This facilitates activity of the spinal cord and accentuates a minimally active reflex. These manoeuvres primarily increase the sensitivity of the muscle spindles and decrease the inhibition of the central nervous system. This, in turn, heightens or exaggerates the reflex and makes it easier for the examiner to see the reflex. Examples of jendrassik manoeuvres include:

• clenching the teeth
• pushing the knees together
• interlocking the fingers and trying to pull them apart

Table 2 highlights the most commonly used deep tendon reflexes in a neurological screen.

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 the 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

A 5-point scale is used to grade deep tendon reflexes and characterise the stretch reflex response (see 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 neurone
1	Somewhat diminished or requires reinforcement	Lower motor neurone
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 they are integrated and disappear. Primitive reflexes are pathological if found in adults as they indicate an underlying nervous system problem. Pathologic reflexes are reversions to primitive responses and indicate loss of cortical inhibition. The most common pathological reflexes tested during neurological screening are highlighted in Table 4. Positive results indicate an upper motor neurone lesion.

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 the plantar surface of the foot from heel to great toe, starting from the lateral side and sweeping across to the medial side at the ball of the foot.	Extension of the great toe
Clonus Reflex	Pyramidal Tract Lesion	Forcibly and quickly dorsiflex 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

A sensory assessment is commonly used to assess the functionality of the nervous system. It is primarily a subjective examination that requires the patient to be alert and cooperative, so that they can give reliable subjective impressions of various stimuli. Clinicians must understand dermatomes and sensory regions of peripheral cutaneous nerve innervation to conduct a sensory assessment.

• The peripheral cutaneous nerves convey skin sensations via their cutaneous branches as they extend into the trunk.
• Each spinal nerve supplies a specific area of skin, which creates a dermatome pattern of sensory loss for each nerve.
• Clinicians should be able to differentiate a dermatome (nerve root) from the sensory distribution of a peripheral nerve.

Examination of peripheral cutaneous innervation over dermatomes is only necessary when suggested by the history. Although a conclusive diagnosis cannot be reached through sensory testing alone, it remains an essential tool to help localise the impairment.

Key difference between Dermatome and Peripheral Cutaneous Nerve Innervation

• Dermatome is an area of the skin that is innervated by a single spinal nerve.
• Peripheral cutaneous innervation is an area of the skin innervated by a specific cutaneous nerve.

The primary modalities that should be included as part of a basic neurologic screen include light touch, deep touch or pressure, temperature, pain and proprioception.

To learn more about sensation and the sensory pathways, see Sensation.

Dermatomes

Dermatomes are areas of the skin which are innervated by the afferent nerve fibres from the dorsal root of a specific nerve root.

Several dermatome maps are commonly employed in practice, including the Foerster Map and Keegan and Garret Map, which are recognised and often used within rehabilitation settings. While valuable, there is some evidence suggesting that current dermatome maps are inaccurate and based on flawed studies. Moreover, dermatomes vary significantly between maps and even among individuals, and there is often overlap between dermatomes. To maintain consistency in your approach to dermatome testing:

• determine which dermatome map you are going to use
• consistently use this in all your testing
• communicate what map you have used with other healthcare professionals

The history will usually determine whether an examination of dermatomes is required. During testing, the patient is asked to indicate any area of altered sensation, including its limits. The examination should focus on the region identified in the history rather than including every dermatome. Each side should be tested (bilateral sensory testing), and testing should follow a standard procedure.

• Light touch has typically been used for sensory testing. However, recent evidence suggests that circumferential pin-prick testing should be used for primary dermatome testing if peripheral neuropathy is suspected. This should be followed by thermal testing in the area of maximal pain if pin-prick testing is normal. This evaluates 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 extending 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. Watch the following videos of the lower limbs and upper limbs to see how to test circumferentially. They also suggest a star-shaped pattern can be used to better delineate the sensory loss. Watch this video on star delineation here.
• Patients confirm recognisable sensations, whether they be light touch, sharp, temperature etc.

You can read more about dermatomes here.

Motor Assessment

When performing a motor examination, it is important to remember that weakness can result from a lesion at any point in the nervous system, including the cerebral hemispheres, brain stem, spinal cord, anterior horn cell, nerve root (myotome), peripheral nerves, neuromuscular junction, or muscle. The motor assessment typically involves manual myotome testing of reference muscles. This can be supplemented by a functional assessment and by identifying areas of muscular atrophy. It is important to note, however, that the manual testing of these muscles will not typically differentiate between nerve root or distal nerve trunk compromise.

Myotomes

Myotomes represent a group of muscles that are innervated by a single specific nerve root. Essentially, myotomes are the motor equivalent to dermatomes. Myotome testing is performed using manual muscle testing - this involves testing the sustained isometric contraction of a specific group of muscles. Table 5 details which movements have the strongest association with each myotome.

Table 5. Myotomes

Nerve Root	Upper Limb Movement	Nerve Root	Lower Limb Movement
C2	Neck Flexion	L2	Hip Flexion
C3	Neck Extension	L3	Knee Extension
C4	Shoulder Elevation	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

Bender et al. recommend that further testing should be completed if weakness is 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. In this example, to assist the clinical reasoning process, the clinician would test a radial nerve muscle that is not innervated by the C8 nerve root (e.g., brachioradialis) and then test a muscle that is innervated by the C8 nerve root but not the radial nerve (e.g., 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 indicate 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:

• The 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.
• Determine whether the 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.