32 Questions
Which nerve root innervates the neck area?
C3
Which nerve root provides sensation to the belly button?
T10
Which nerve root innervates the upper portion of the arm and shoulder?
C5
Which dermatome covers the medial part of the lower leg?
L4
Which nerve root is responsible for sensation in the palm of the hands?
C8
What type of somatosensory symptoms are associated with lesions in the spinothalamic pathway?
Loss of pain and temperature sensation
Which nerve is primarily responsible for sensory input from the face in the context of somatosensory pathways?
Trigeminal nerve (CN V)
In brown sequard syndrome, what sensory deficits are typically observed?
Ipsilateral loss of vibration and joint position sense
What is a common cause of a transverse spinal cord lesion?
Syringomyelia
Which thalamic nucleus plays a significant role in processing somatosensory information?
Ventral posterior medial (VPM) nucleus
What type of deficits are seen with central cord lesions affecting the spinothalamic fibers crossing in the ventral commissure?
Bilateral regions of suspended sensory loss to pain and temperature
What is the second most common cause of vestibular neuritis?
Meniere’s Disease
Which condition can lead to blurry vision in cases of bilateral vestibular loss?
Meniere’s disease (bilateral)
In central vestibular lesions, what reflex involves the medial vestibular nucleus?
Opto-kinetic reflex
Which combination of tests can help indicate whether a vestibular lesion is peripheral or central?
OKR and VOR
What does an abnormal VOR but normal OKR indicate about a vestibular injury?
Peripheral system damage only
What is the function of the primary sensory neuron in the posterior column pathway?
To transmit fine touch, vibration, and proprioception signals
Which of the following structures is formed by second-order sensory neurons after decussation in the caudal medulla?
Medial lemniscus
Which type of sensory information is carried by the spinothalamic tract?
Pain
What is the term used for the inability to recognize objects by touch?
Asterognosis
What are the consequences of damage to the primary sensory neuron?
Loss of position and vibration sense, and discriminatory touch
Which of the following pathways carries information about upper and lower extremities?
Gracile fasciculus and cuneate fasciculus
Which type of syndrome causes loss of pain and temperature sensation unilaterally?
Anterior cord syndrome
Which vestibular sensory neuron is responsible for controlling head and neck positions?
Medial Vestibular Nucleus (MVN)
Which vestibular sensory neuron projects via the medial longitudinal fasciculus (MLF) to the oculo-motor nucleus, trochlear nucleus, and abducens nucleus?
Superior Vestibular Nucleus (SVN) and Medical Vestibular Nucleus (MVN)
Which test is used to measure nystagmus in response to short-duration auditory tones or clicks?
VEMPS
Which organ in the vestibular system detects angular acceleration?
Semicircular canals
Which vestibular sensory neuron is responsible for maintaining balance and extensor tone in limbs?
Lateral Vestibular Nucleus (LVN)
Which type of syndrome causes vibration and position sense loss below the level of lesion?
Posterior cord syndrome
Which test is used to measure nystagmus in all planes of motion?
Head impulse test
Which vestibular sensory neuron controls the vestibulo-ocular reflex (VOR)?
Superior Vestibular Nucleus (SVN)
Which organ in the vestibular system is gravity-sensitive due to the movement of stimulation?
Utricle and saccule
Study Notes
Dermatomes and Sensory Pathways
- Dermatomes are sensory regions of the skin innervated by a nerve root.
- Major dermatomes include:
- C2: greater and lesser occipital nerve (head)
- C3: neck
- C4: top of shoulder (collarbone)
- C5: upper portion of arm/shoulder area
- C6-C7: upper half of lower arm and hands
- C7 & C8: palm of hands
- T4: nipple area (chest area)
- T10: belly button
- L3: knee
- S1: small toe, lateral foot, side of the calf
- L4: medial part of the lower leg
Sensory Pathways
- PCML (Posterior Column-Medial Lemniscus) pathway:
- Large diameter myelinated axons carrying information about proprioception, vibration, and light/fine touch
- Enter the spinal cord via the medial portion of the dorsal root entry level/zone
- Axons enter the ipsilateral posterior column to ascend to the posterior column nuclei in the medulla
- Maintain somatotopic organization (legs = lateral, arms = medial)
- Anterolateral pathway (Spinothalamic tract):
- Carry information about pain and temperature sensation and some extent of crude touch
- Test pain by the end of a toothpick and lightly touching the skin to see if an individual feels the sharpness
Trigeminal Nerve
- Innervates the face
- Main pathway to the thalamus is the trigeminothalamic tract
- Main thalamic nucleus: VPM (ventral posterior medial nucleus)
- Runs from lateral pons and medulla
- Functions: contains 3 nuclei that receive general somatic sensory inputs from CN V and other cranial nerves
Spinal Cord Syndromes
- Hemicord syndrome (Brown-Séquard syndrome):
- Interruption of the posterior column causes ipsilateral loss of vibration and joint position sense
- Contralateral loss of pain and temperature sensation in the anterolateral system, which is 2-3 segments below the lesion
- Transverse lesions:
- Sensory loss and pain = ipsilateral to the lesion
- Positive LMN symptoms at the level of the lesion
- Central cord syndrome:
- Small lesion: damage to spinothalamic fibers crossing in the ventral commissure causes bilateral regions of suspended sensory loss to pain and temperature
- Causes: syringomyelia (fluid-filled cavity in the spinal cord), tumors, and MS
Primary Sensory Neurons
- Bifurcate: ascending axons enter the posterior column
- Synapse on the respective nucleus
- Second-order sensory neurons cross the midline in the caudal medulla and synapse in the thalamus
- Decussate as internal arcuate fibers and then form the medial lemniscus on the other side of the medulla
PC-ML Pathway Symptoms
- Loss of position and vibration sense (limb orientation)
- Loss of discriminatory touch (2-point discrimination)
- Crude touch preserved
- Astereognosis: inability to recognize objects by touch
- Sensory 'ataxia': unsteady balance and gait, poorly coordinated movements
Vestibular System
- Cochlea: detects sound waves
- Semicircular canals: detect angular acceleration
- Utricle and saccule hair cells in the ampulla are all oriented in the same direction
- Otolith organs detect linear acceleration and are gravity-sensitive
- Vestibular sensory neurons: lateral vestibular nucleus (LVN), medial vestibular nucleus (MVN), superior vestibular nucleus (SVN), and inferior vestibular nucleus (IVN)
Learn about major dermatomes for legs & feet, arms & hands, and trunk. Understanding dermatomes is useful in identifying the site of a lesion. Explore how sensory regions of the skin are innervated by specific nerve roots.
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