Module 11: The Neurological Exam

Lesson 4: The Sensory and Motor Exams

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Mỗi bài học (lesson) bao gồm 4 phần chính: Thuật ngữ, Luyện Đọc, Luyện Nghe, và Bàn Luận.
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Dưới đây là danh sách những thuật ngữ Y khoa của module The Neurological Exam.
Khái quát được số lượng thuật ngữ sẽ xuất hiện trong bài đọc và nghe sẽ giúp bạn thoải mái tiêu thụ nội dung hơn. Sau khi hoàn thành nội dung đọc và nghe, bạn hãy quay lại đây và luyện tập (practice) để quen dần các thuật ngữ này. Đừng ép bản thân phải nhớ các thuật ngữ này vội vì bạn sẽ gặp và ôn lại danh sách này trong những bài học (lesson) khác của cùng một module.

Medical Terminology: The Neurological Exam

accommodation
in vision, a change in the ability of the eye to focus on objects at different distances
accommodation–convergence reflex
coordination of somatic control of the medial rectus muscles of either eye with the parasympathetic control of the ciliary bodies to maintain focus while the eyes converge on visual stimuli near to the face
anterograde amnesia
inability to form new memories from a particular time forward
aphasia
loss of language function
ataxia
movement disorder related to damage of the cerebellum characterized by loss of coordination in voluntary movements
Babinski sign
dorsiflexion of the foot with extension and splaying of the toes in response to the plantar reflex, normally suppressed by corticospinal input
cerebrocerebellum
lateral regions of the cerebellum; named for the significant input from the cerebral cortex
check reflex
response to a release in resistance so that the contractions stop, or check, movement
clasp-knife response
sign of UMN disease when a patient initially resists passive movement of a muscle but will quickly release to a lower state of resistance
conduction aphasia
loss of language function related to connecting the understanding of speech with the production of speech, without either specific function being lost
conductive hearing
hearing dependent on the conduction of vibrations of the tympanic membrane through the ossicles of the middle ear
conjugate gaze
coordinated movement of the two eyes simultaneously in the same direction
convergence
in vision, the movement of the eyes so that they are both pointed at the same point in space, which increases for stimuli that are closer to the subject
coordination exam
major section of the neurological exam that assesses complex, coordinated motor functions of the cerebellum and associated motor pathways
cortico-ponto-cerebellar pathway
projection from the cerebral cortex to the cerebellum by way of the gray matter of the pons
cranial nerve exam
major section of the neurological exam that assesses sensory and motor functions of the cranial nerves and their associated central and peripheral structures
cytoarchitecture
study of a tissue based on the structure and organization of its cellular components; related to the broader term, histology
deep tendon reflex
another term for stretch reflex, based on the elicitation through deep stimulation of the tendon at the insertion
diplopia
double vision resulting from a failure in conjugate gaze
edema
fluid accumulation in tissue; often associated with circulatory deficits
embolus
obstruction in a blood vessel such as a blood clot, fatty mass, air bubble, or other foreign matter that interrupts the flow of blood to an organ or some part of the body
episodic memory
memory of specific events in an autobiographical sense
expressive aphasia
loss of the ability to produce language; usually associated with damage to Broca’s area in the frontal lobe
extrinsic muscles of the tongue
muscles that are connected to other structures, such as the hyoid bone or the mandible, and control the position of the tongue
fasciculation
small muscle twitch as a result of spontaneous activity from an LMN
fauces
opening from the oral cavity into the pharynx
fibrillation
in motor responses, a spontaneous muscle action potential that occurs in the absence of neuromuscular input, resulting from LMN lesions
flaccid paralysis
loss of voluntary muscle control and muscle tone, as the result of LMN disease
flaccidity
presentation of a loss of muscle tone, observed as floppy limbs or a lack of resistance to passive movement
flocculonodular lobe
lobe of the cerebellum that receives input from the vestibular system to help with balance and posture
gait
rhythmic pattern of alternating movements of the lower limbs during locomotion
gait exam
major section of the neurological exam that assesses the cerebellum and descending pathways in the spinal cord through the coordinated motor functions of walking; a portion of the coordination exam
gnosis
in a neurological exam, intuitive experiential knowledge tested by interacting with common objects or symbols
graphesthesia
perception of symbols, such as letters or numbers, traced in the palm of the hand
hemisection
cut through half of a structure, such as the spinal cord
hemorrhagic stroke
disruption of blood flow to the brain caused by bleeding within the cranial vault
hyperflexia
overly flexed joints
hypotonicity
low muscle tone, a sign of LMN disease
hypovolemia
decrease in blood volume
inferior cerebellar peduncle (ICP)
input to the cerebellum, largely from the inferior olive, that represents sensory feedback from the periphery
inferior olive
large nucleus in the medulla that receives input from sensory systems and projects into the cerebellar cortex
internuclear ophthalmoplegia
deficit of conjugate lateral gaze because the lateral rectus muscle of one eye does not contract resulting from damage to the abducens nerve or the MLF
intorsion
medial rotation of the eye around its axis
intrinsic muscles of the tongue
muscles that originate out of, and insert into, other tissues within the tongue and control the shape of the tongue
ischemic stroke
disruption of blood flow to the brain because blood cannot flow through blood vessels as a result of a blockage or narrowing of the vessel
jaw-jerk reflex
stretch reflex of the masseter muscle
localization of function
principle that circumscribed anatomical locations are responsible for specific functions in an organ system
medial longitudinal fasciculus (MLF)
fiber pathway that connects structures involved in the control of eye and head position, from the superior colliculus to the vestibular nuclei and cerebellum
mental status exam
major section of the neurological exam that assesses cognitive functions of the cerebrum
middle cerebellar peduncle (MCP)
large, white-matter bridge from the pons that constitutes the major input to the cerebellar cortex
motor exam
major section of the neurological exam that assesses motor functions of the spinal cord and spinal nerves
neurological exam
clinical assessment tool that can be used to quickly evaluate neurological function and determine if specific parts of the nervous system have been affected by damage or disease
paramedian pontine reticular formation (PPRF)
region of the brain stem adjacent to the motor nuclei for gaze control that coordinates rapid, conjugate eye movements
paresis
partial loss of, or impaired, voluntary muscle control
plantar reflex
superficial reflex initiated by gentle stimulation of the sole of the foot
praxis
in a neurological exam, the act of doing something using ready knowledge or skills in response to verbal instruction
procedural memory
memory of how to perform a specific task
pronator drift
sign of contralateral corticospinal lesion when the one arm will drift into a pronated position when held straight out with the palms facing upward
receptive aphasia
loss of the ability to understand received language, such as what is spoken to the subject or given in written form
red nucleus
nucleus in the midbrain that receives output from the cerebellum and projects onto the spinal cord in the rubrospinal tract
retrograde amnesia
loss of memories before a particular event
Rinne test
use of a tuning fork to test conductive hearing loss versus sensorineural hearing loss
Romberg test
test of equilibrium that requires the patient to maintain a straight, upright posture without visual feedback of position
rubrospinal tract
descending tract from the red nucleus of the midbrain that results in modification of ongoing motor programs
saccade
small, rapid movement of the eyes used to locate and direct the fovea onto visual stimuli
sensorineural hearing
hearing dependent on the transduction and propagation of auditory information through the neural components of the peripheral auditory structures
sensory exam
major section of the neurological exam that assesses sensory functions of the spinal cord and spinal nerves
short-term memory
capacity to retain information actively in the brain for a brief period of time
Snellen chart
standardized arrangement of letters in decreasing size presented to a subject at a distance of 20 feet to test visual acuity
spasticity
increased contraction of a muscle in response to resistance, often resulting in hyperflexia
spinocerebellar tract
ascending fibers that carry proprioceptive input to the cerebellum used in maintaining balance and coordinated movement
spinocerebellum
midline region of the cerebellum known as the vermis that receives proprioceptive input from the spinal cord
stereognosis
perception of common objects placed in the hand solely on the basis of manipulation of that object in the hand
stroke
(also, cerebrovascular accident (CVA)) loss of neurological function caused by an interruption of blood flow to a region of the central nervous system
superficial reflex
reflexive contraction initiated by gentle stimulation of the skin
superior cerebellar peduncle (SCP)
white-matter tract representing output of the cerebellum to the red nucleus of the midbrain
transient ischemic attack (TIA)
temporary disruption of blood flow to the brain in which symptoms occur rapidly but last only a short time
vermis
prominent ridge along the midline of the cerebellum that is referred to as the spinocerebellum
vestibulo-ocular reflex (VOR)
reflex based on connections between the vestibular system and the cranial nerves of eye movements that ensures that images are stabilized on the retina as the head and body move
vestibulocerebellum
flocculonodular lobe of the cerebellum named for the vestibular input from the eighth cranial nerve
Weber test
use of a tuning fork to test the laterality of hearing loss by placing it at several locations on the midline of the skull
Wernicke’s area
region at the posterior end of the lateral sulcus in which speech comprehension is localized
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Dưới đây là các bài văn nằm ở bên trái. Ở bên phải là các bài luyện tập (practice) để đánh giá khả năng đọc hiểu của bạn. Sẽ khó khăn trong thời gian đầu nếu vốn từ vựng của bạn còn hạn chế, đặc biệt là từ vựng Y khoa. Hãy kiên nhẫn và đọc nhiều nhất có kể, lượng kiến thức tích tụ dần sẽ giúp bạn đọc thoải mái hơn.
Connections between the body and the CNS occur through the spinal cord. The cranial nerves connect the head and neck directly to the brain, but the spinal cord receives sensory input and sends motor commands out to the body through the spinal nerves. Whereas the brain develops into a complex series of nuclei and fiber tracts, the spinal cord remains relatively simple in its configuration (Figure 1). From the initial neural tube early in embryonic development, the spinal cord retains a tube-like structure with gray matter surrounding the small central canal and white matter on the surface in three columns. The dorsal, or posterior, horns of the gray matter are mainly devoted to sensory functions whereas the ventral, or anterior, and lateral horns are associated with motor functions. In the white matter, the dorsal column relays sensory information to the brain, and the anterior column is almost exclusively relaying motor commands to the ventral horn motor neurons. The lateral column, however, conveys both sensory and motor information between the spinal cord and brain.
The general senses are distributed throughout the body, relying on nervous tissue incorporated into various organs. Somatic senses are incorporated mostly into the skin, muscles, or tendons, whereas the visceral senses come from nervous tissue incorporated into the majority of organs such as the heart or stomach. The somatic senses are those that usually make up the conscious perception of the how the body interacts with the environment. The visceral senses are most often below the limit of conscious perception because they are involved in homeostatic regulation through the autonomic nervous system.

The sensory exam tests the somatic senses, meaning those that are consciously perceived. Testing of the senses begins with examining the regions known as dermatomes that connect to the cortical region where somatosensation is perceived in the postcentral gyrus. To test the sensory fields, a simple stimulus of the light touch of the soft end of a cotton-tipped applicator is applied at various locations on the skin. The spinal nerves, which contain sensory fibers with dendritic endings in the skin, connect with the skin in a topographically organized manner, illustrated as dermatomes (Figure 2). For example, the fibers of eighth cervical nerve innervate the medial surface of the forearm and extend out to the fingers. In addition to testing perception at different positions on the skin, it is necessary to test sensory perception within the dermatome from distal to proximal locations in the appendages, or lateral to medial locations in the trunk. In testing the eighth cervical nerve, the patient would be asked if the touch of the cotton to the fingers or the medial forearm was perceptible, and whether there were any differences in the sensations.

Other modalities of somatosensation can be tested using a few simple tools. The perception of pain can be tested using the broken end of the cotton-tipped applicator. The perception of vibratory stimuli can be testing using an oscillating tuning fork placed against prominent bone features such as the distal head of the ulna on the medial aspect of the elbow. When the tuning fork is still, the metal against the skin can be perceived as a cold stimulus. Using the cotton tip of the applicator, or even just a fingertip, the perception of tactile movement can be assessed as the stimulus is drawn across the skin for approximately 2–3 cm. The patient would be asked in what direction the stimulus is moving. All of these tests are repeated in distal and proximal locations and for different dermatomes to assess the spatial specificity of perception. The sense of position and motion, proprioception, is tested by moving the fingers or toes and asking the patient if they sense the movement. If the distal locations are not perceived, the test is repeated at increasingly proximal joints.

The various stimuli used to test sensory input assess the function of the major ascending tracts of the spinal cord. The dorsal column pathway conveys fine touch, vibration, and proprioceptive information, whereas the spinothalamic pathway primarily conveys pain and temperature. Testing these stimuli provides information about whether these two major ascending pathways are functioning properly. Within the spinal cord, the two systems are segregated. The dorsal column information ascends ipsilateral to the source of the stimulus and decussates in the medulla, whereas the spinothalamic pathway decussates at the level of entry and ascends contralaterally. The differing sensory stimuli are segregated in the spinal cord so that the various subtests for these stimuli can distinguish which ascending pathway may be damaged in certain situations.

Whereas the basic sensory stimuli are assessed in the subtests directed at each submodality of somatosensation, testing the ability to discriminate sensations is important. Pairing the light touch and pain subtests together makes it possible to compare the two submodalities at the same time, and therefore the two major ascending tracts at the same time. Mistaking painful stimuli for light touch, or vice versa, may point to errors in ascending projections, such as in a hemisection of the spinal cord that might come from a motor vehicle accident.

Another issue of sensory discrimination is not distinguishing between different submodalities, but rather location. The two-point discrimination subtest highlights the density of sensory endings, and therefore receptive fields in the skin. The sensitivity to fine touch, which can give indications of the texture and detailed shape of objects, is highest in the fingertips. To assess the limit of this sensitivity, two-point discrimination is measured by simultaneously touching the skin in two locations, such as could be accomplished with a pair of forceps. Specialized calipers for precisely measuring the distance between points are also available. The patient is asked to indicate whether one or two stimuli are present while keeping their eyes closed. The examiner will switch between using the two points and a single point as the stimulus. Failure to recognize two points may be an indication of a dorsal column pathway deficit.

Similar to two-point discrimination, but assessing laterality of perception, is double simultaneous stimulation. Two stimuli, such as the cotton tips of two applicators, are touched to the same position on both sides of the body. If one side is not perceived, this may indicate damage to the contralateral posterior parietal lobe. Because there is one of each pathway on either side of the spinal cord, they are not likely to interact. If none of the other subtests suggest particular deficits with the pathways, the deficit is likely to be in the cortex where conscious perception is based. The mental status exam contains subtests that assess other functions that are primarily localized to the parietal cortex, such as stereognosis and graphesthesia.

A final subtest of sensory perception that concentrates on the sense of proprioception is known as the Romberg test. The patient is asked to stand straight with feet together. Once the patient has achieved their balance in that position, they are asked to close their eyes. Without visual feedback that the body is in a vertical orientation relative to the surrounding environment, the patient must rely on the proprioceptive stimuli of joint and muscle position, as well as information from the inner ear, to maintain balance. This test can indicate deficits in dorsal column pathway proprioception, as well as problems with proprioceptive projections to the cerebellum through the spinocerebellar tract.
The skeletomotor system is largely based on the simple, two-cell projection from the precentral gyrus of the frontal lobe to the skeletal muscles. The corticospinal tract represents the neurons that send output from the primary motor cortex. These fibers travel through the deep white matter of the cerebrum, then through the midbrain and pons, into the medulla where most of them decussate, and finally through the spinal cord white matter in the lateral (crossed fibers) or anterior (uncrossed fibers) columns. These fibers synapse on motor neurons in the ventral horn. The ventral horn motor neurons then project to skeletal muscle and cause contraction. These two cells are termed the upper motor neuron (UMN) and the lower motor neuron (LMN). Voluntary movements require these two cells to be active.

The motor exam tests the function of these neurons and the muscles they control. First, the muscles are inspected and palpated for signs of structural irregularities. Movement disorders may be the result of changes to the muscle tissue, such as scarring, and these possibilities need to be ruled out before testing function. Along with this inspection, muscle tone is assessed by moving the muscles through a passive range of motion. The arm is moved at the elbow and wrist, and the leg is moved at the knee and ankle. Skeletal muscle should have a resting tension representing a slight contraction of the fibers. The lack of muscle tone, known as hypotonicity or flaccidity, may indicate that the LMN is not conducting action potentials that will keep a basal level of acetylcholine in the neuromuscular junction.

If muscle tone is present, muscle strength is tested by having the patient contract muscles against resistance. The examiner will ask the patient to lift the arm, for example, while the examiner is pushing down on it. This is done for both limbs, including shrugging the shoulders. Lateral differences in strength—being able to push against resistance with the right arm but not the left—would indicate a deficit in one corticospinal tract versus the other. An overall loss of strength, without laterality, could indicate a global problem with the motor system. Diseases that result in UMN lesions include cerebral palsy or MS, or it may be the result of a stroke. A sign of UMN lesion is a negative result in the subtest for pronator drift. The patient is asked to extend both arms in front of the body with the palms facing up. While keeping the eyes closed, if the patient unconsciously allows one or the other arm to slowly relax, toward the pronated position, this could indicate a failure of the motor system to maintain the supinated position.
Reflexes combine the spinal sensory and motor components with a sensory input that directly generates a motor response. The reflexes that are tested in the neurological exam are classified into two groups. A deep tendon reflex is commonly known as a stretch reflex (see the chapter on The Somatic Nervous System ), and is elicited by a strong tap to a tendon, such as in the knee-jerk reflex. A superficial reflex is elicited through gentle stimulation of the skin and causes contraction of the associated muscles.

For the arm, the common reflexes to test are of the biceps, brachioradialis, triceps, and flexors for the digits. For the leg, the knee-jerk reflex of the quadriceps is common, as is the ankle reflex for the gastrocnemius and soleus. The tendon at the insertion for each of these muscles is struck with a rubber mallet. The muscle is quickly stretched, resulting in activation of the muscle spindle that sends a signal into the spinal cord through the dorsal root. The fiber synapses directly on the ventral horn motor neuron that activates the muscle, causing contraction. The reflexes are physiologically useful for stability. If a muscle is stretched, it reflexively contracts to return the muscle to compensate for the change in length. In the context of the neurological exam, reflexes indicate that the LMN is functioning properly.

The most common superficial reflex in the neurological exam is the plantar reflex that tests for the Babinski sign on the basis of the extension or flexion of the toes at the plantar surface of the foot. The plantar reflex is commonly tested in newborn infants to establish the presence of neuromuscular function. To elicit this reflex, an examiner brushes a stimulus, usually the examiner’s fingertip, along the plantar surface of the infant’s foot. An infant would present a positive Babinski sign, meaning the foot dorsiflexes and the toes extend and splay out. As a person learns to walk, the plantar reflex changes to cause curling of the toes and a moderate plantar flexion. If superficial stimulation of the sole of the foot caused extension of the foot, keeping one’s balance would be harder. The descending input of the corticospinal tract modifies the response of the plantar reflex, meaning that a negative Babinski sign is the expected response in testing the reflex. Other superficial reflexes are not commonly tested, though a series of abdominal reflexes can target function in the lower thoracic spinal segments.
Many of the tests of motor function can indicate differences that will address whether damage to the motor system is in the upper or lower motor neurons. Signs that suggest a UMN lesion include muscle weakness, strong deep tendon reflexes, decreased control of movement or slowness, pronator drift, a positive Babinski sign, spasticity, and the clasp-knife response. Spasticity is an excess contraction in resistance to stretch. It can result in hyperflexia, which is when joints are overly flexed. The clasp-knife response occurs when the patient initially resists movement, but then releases, and the joint will quickly flex like a pocket knife closing.

A lesion on the LMN would result in paralysis, or at least partial loss of voluntary muscle control, which is known as paresis. The paralysis observed in LMN diseases is referred to as flaccid paralysis, referring to a complete or partial loss of muscle tone, in contrast to the loss of control in UMN lesions in which tone is retained and spasticity is exhibited. Other signs of an LMN lesion are fibrillation, fasciculation, and compromised or lost reflexes resulting from the denervation of the muscle fibers.

OpenStax. (2022). Anatomy and Physiology 2e. Rice University. Retrieved June 15, 2023. ISBN-13: 978-1-711494-06-7 (Hardcover) ISBN-13: 978-1-711494-05-0 (Paperback) ISBN-13: 978-1-951693-42-8 (Digital). License: Attribution 4.0 International (CC BY 4.0). Access for free at openstax.org.

The surface of the skin can be divided into topographic regions that relate to the location of sensory endings in the skin based on the spinal nerve that contains those fibers. (credit: modification of work by Mikael Häggström)

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Dưới đây là video và các luyện tập (practice) của bài này. Nghe là một kĩ năng khó, đặc biệt là khi chúng ta chưa quen nội dung và chưa có nhạy cảm ngôn ngữ. Nhưng cứ đi thật chậm và đừng bỏ cuộc.
Xem video và cảm nhận nội dung bài. Bạn có thể thả trôi, cảm nhận dòng chảy ngôn ngữ và không nhất thiết phải hiểu toàn bộ bài. Bên dưới là script để bạn khái quát nội dụng và tra từ mới.
Script:
  1. The sensory and motor exams assess function related to the spinal cord and the nerves connected to it.
  2. Sensory functions are associated with the dorsal regions of the spinal cord, whereas motor function is associated with the ventral side.
  3. Localizing damage to the spinal cord is related to assessments of the peripheral projections mapped to dermatomes.
  4. Sensory tests address the various submodalities of the somatic senses: touch, temperature, vibration, pain, and proprioception.
  5. Results of the subtests can point to trauma in the spinal cord gray matter, white matter, or even in connections to the cerebral cortex.
  6. Motor tests focus on the function of the muscles and the connections of the descending motor pathway.
  7. Muscle tone and strength are tested for upper and lower extremities.
  8. Input to the muscles comes from the descending cortical input of upper motor neurons and the direct innervation of lower motor neurons.
  9. Reflexes can either be based on deep stimulation of tendons or superficial stimulation of the skin.
  10. The presence of reflexive contractions helps to differentiate motor disorders between the upper and lower motor neurons.
  11. The specific signs associated with motor disorders can establish the difference further, based on the type of paralysis, the state of muscle tone, and specific indicators such as pronator drift or the Babinski sign.
  12. The Babinski sign is a neurological reflex characterized by the extension of the big toe and fanning of the other toes in response to the sole of the foot being stroked.
  13. This indicates upper motor neuron lesion constituting damage to the corticospinal tract.
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