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.

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 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.

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 Jenrassick 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, by countering some of the normal descending inhibition the brain sends to the reflex arc.

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

Table.1 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 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

Superficial Reflexes

Table.3 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

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.

Pathological Reflexes

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

Reflex	Nerve Supply	Segmental Innervation	Description of Action	Response
Hoffman's Sign			Flicking the distal phalanx of the index finger	Clawing movement of the fingers and thumb
Babinski's Reflex	Tibial	S1-2	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

Sensory Assessment

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 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 used in healthcare and accounts for the dermatomes used in the American Spinal Cord Injury Association Impairment Scale (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.

Table.5 ASIA Scale Dermatomes from the 1933 Foerster Map

Nerve Root	Description of Key Points for Sensory Testing
C2	1 cm lateral to Occipital Protuberance
C3	Supraclavicular Fossa at Midclavicular Line
C4	Over Acromioclavicular Joint
C5	Lateral Side Antecubital Fossa just Proximal to Elbow Crease
C6	Dorsal Surface of Proximal Phalanx of the Thumb
C7	Dorsal Surface of Proximal Phalanx of the Middle Finger
C8	Dorsal Surface of Proximal Phalanx of the Little Finger
T1	Medial Side Antecubital Fossa, just Proximal to Medical Epicondyle of Humerus
T2	Apex of Axilla
T3	Midclavicular Line and 3rd Intercostal Space
T4	Midclavicular Line and 4th Intercostal Space at Nipple Line
T5	Midclavicular Line and 5th Intercostal Space Midway between T4 & T6
T6	Midclavicular Line and 6th Intercostal Space at the level of Xiphisternum
T7	Midclavicular Line and 7th Intercostal Space Midway between T6 & T8 - Quarter Distance between Level Xiphisternum & Umbilicus
T8	Midclavicular Line and 8th Intercostal Space Midway between T6 & T10- Half Distance between Level Xiphisternum & Umbilicus
T9	Midclavicular Line and 9th Intercostal Space Midway between T8 & T10 - Three Quarters Distance between Level Xiphisternum & Umbilicus
T10	Midclavicular Line and 10th Intercostal Space at the Level of Umbilicus
T11	Midclavicular Line and 11th Intercostal Space Midway between T10 & T12 - Midway between Level of Umbilicus & Inguinal Ligament
T12	Midclavicular Line Over Midpoint Inguinal Ligament
L1	Midway between Sensory Point at T12 & L1
L2	Anterior-Medial Thigh at the Midpoint drawn connecting Midpoint of Inguinal Ligament & Medial Femoral Condyle
L3	Medial femoral Condyle above the Knee
L4	Medial Malleolus
L5	Dorsal Foot at 3rd Metatarsal Phalangeal Joint
S1	Lateral Aspect of Calcaneus
S2	Midpoint of Popliteal Fossa
S3	Over Ischial Tuberosity or Infragluteal Fold
S4 - 5	Perianal Area < 1cm Lateral to Mucocutaneous Junction

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. 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

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 and may show a characteristic "upper motor neurone pattern" or "lower motor neurone pattern".

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	Ana l 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 the mechanism of injury, signs and symptoms and clinical reasoning in deciding when and what to assess.

References