Sensory Syndromes PDF - 3rd Year of Medicine - 2024/2025

SENSORY SYNDROMES GENERAL PATHOLOGY. 3rd year of Medicine 2024/2025 Ana Checa-Ros MD, PhD Department of Medicine & Surgery [email protected] INDEX Types of Sensations Anatomical Review Sensory Syndromes 1. TYPES OF SENSATIONS Pain Touch Temperature Vibration Proprioception Join...

SENSORY SYNDROMES GENERAL PATHOLOGY. 3rd year of Medicine 2024/2025 Ana Checa-Ros MD, PhD Department of Medicine & Surgery [email protected] INDEX Types of Sensations Anatomical Review Sensory Syndromes 1. TYPES OF SENSATIONS Pain Touch Temperature Vibration Proprioception Joint motion and limb position Cortical sensations They are always tested with the patient's eyes closed Two-point discrimination: ability to distinguish two compass points simultaneously applied to the skin Tactile Recognition: ability to recognise common objects (key, coin) placed on the hand Graphesthesia: ability to identify letters or numbers traced on the hand Localisation: ability to accurately point to a spot on the body just touched by the clinician 1.1. Classification Unlike other sensations, vibration, proprioception and cortical sensations require the integrity of the contralateral cerebral sensory cortex to be perceived correctly Pain, temperature and touch, however, are processed at the contralateral thalamus 2. ANATOMICAL REVIEW 2.1. Spinal Nerves SENSORY MOTOR 2.1. Spinal nerves Each spinal nerve has an anterior and a posterior root Anterior roots: they are composed of the motor nerve fibres, which transmit motor information; they originate from the anterior horns of the spinal cord and exit the spinal cord towards the limb/trunk muscles Posterior roots: they carry sensory information from the sensory receptors to the posterior horns of the spinal cord; they have a sensory ganglion attached 2.2. Sensory Pathways Spinothalamic Pathway: It carries information about pain, temperature and coarse (crude) touch, such as itching and tickling sensations The fibres arrive through the posterior horns; they decussate (crossing to the opposite side) at the level of the spinal cord, anterior to the central canal, and ascend towards the thalamus The spinothalamic fibres cross the central grey matter of the spinal cord and ascend on the opposite side of the cord 2.2. Sensory Pathways Dorsal Column-Medial Lemniscus (DCML) Pathway: It carries information about vibration, proprioception and fine touch The fibres (Cuneate and Gracile Fasciculi) arrive through the posterior horns; they ascend ipsilaterally in the posterior part of the spinal cord; they then decussate (cross to the opposite side) at the lower medulla in the brainstem; afterwards, they travel to synapse in the thalamus and then in the parietal cortex The DCML pathway ascends on the ipsilateral side of the spinal cord and decussate in the medulla SPINAL CORD SECTION DESCENDING TRACTS (MOTOR) ASCENDING TRACTS (SENSORY) Lateral corticospinal tract DCML pathway Vibration Fine touch Proprioception Lateral spinothalamic tract Pain Temperature Spinocerebellar tracts Anterior spinothalamic tract Anterior corticospinal tract Coarse Touch 2.2. Sensory Pathways Head and facial sensations are conveyed by the three divisions of the trigeminal nerve (CN V): ophthalmic division; maxillary division; and mandibular division The trigeminal nerve carries afferent stimuli of pain, temperature and touch to the trigeminal nucleus in the pons, where it decussates to contralaterally ascend to the thalamus and, finally, to the somatosensory cortex in the parietal lobe Trigeminal Nerve (CN V)  Somatosensory cortex Sensory Pathways Thalamus CN V nucleus CN V ganglion Pons Trigeminal Nerve DCML Pathway CN V nucleus Cuneate and Gracile Fasciculi Medulla Dorsal Ganglion Spinothalamic Tract The somatosensory cortex Posterior Root receives sensations from the opposite side of the body Spinal Cord 2.3. Somatosensory Cortex 3. SENSORY SYNDROMES  Localisation-Based Classification Peripheral Somatosensory Dorsal Root Spinal Cord Brainstem Thalamus Nerve Cortex 3.1. Peripheral Nerve A lesion affecting sensory fibres in a peripheral nerve is accompanied by sensory impairment of all modalities in the corresponding anatomical distribution (dermatome) Distribution of sensory dermatomes and territories of peripheral nerves. Extracted from: Crash Course Neurology 3.1. Peripheral Nerve If a mixed motor and sensory nerve is involved, the sensory impairment will also be accompanied by motor impairment (muscle weakness, hyporeflexia) Depending on the extension of the lesion, we will distinguish between: Mononeuropathy: damage to a single nerve Polyneuropathy: symmetrical damage to multiple peripheral nerves  Mononeuropathy Polyneuropathy Entrapment of the median nerve at the Chronic alcohol abuse, diabetes mellitus, wrist causing carpal tunnel syndrome demyelinating disorder 3.2. Dorsal Root Disorders of the dorsal root are called dorsal radiculopathies The most common cause of dorsal radiculopathy is a herniated disc Intervertebral disc Herniated disc Roots Peripheral nerve Spinal cord Magnetic resonance imaging of a large lumbar disc herniation Extracted from: Goldman-Cecil Medicine 3.2. Dorsal Root The symptoms of dorsal radiculopathy will depend on the affected root. Generally, they are: Ipsilateral radicular pain: described as electrical or tingling. Ipsilateral hypoesthesia Ipsilateral muscle weakness 3.4. Spinal Cord We distinguish between: A) Posterior Cord Syndrome B) Anterolateral Cord Syndrome C) Central Cord Syndrome  DCML pathway 3.4. Spinal Cord A) Posterior Cord Syndrome: It affects the DCML pathway, with sparing of the spinothalamic and corticospinal fibres Causes: Vitamin B12 deficiency Multiple sclerosis  DCML pathway 3.4. Spinal Cord B) Posterior Cord Syndrome Clinical features: Bilateral impaired vibration and proprioception below the level of the lesion Ataxia (as seen in motor coordination disorders) Motor function and perception of pain and temperature are spared unless the lesion progresses to involve the anterior part of the cord  Corticospinal tract Spinothalamic tracts 3.4. Spinal Cord B) Anterolateral Cord Syndrome It affects the spinothalamic and corticospinal tracts, with sparing of the dorsal columns Causes: Anterior spinal artery occlusion (it normally affects both sides of the spinal cord)  Corticospinal tract Spinothalamic tracts 3.4. Spinal Cord B) Anterolateral Cord Syndrome Clinical features: Bilateral impairment of pain and temperature perceptions below the level of the lesion Paraplegia or tetraplegia with hypotonia and hyporeflexia  Spinothalamic tracts 3.4. Spinal Cord C) Central Cord Syndrome: It affects the spinothalamic fibres at the level of decussation and spares the DCML pathway Causes: Syringomyelia (formation of cavities with cerebrospinal fluid in the spinal cord) Spinal tumours (ependymoma)  Spinothalamic tracts 3.4. Spinal Cord C) Central Cord Syndrome: Clinical features: Dissociated sensory loss: bilateral loss of pain and temperature perception in the segments affected by the lesion, with preservation of touch, vibration and proprioception If the lesion expands sufficiently, it might eventually involve the corticospinal tracts and cause LMN signs below the lesion  POSTERIOR CORD ANTEROLATERAL CORD CENTRAL CORD SYNDROME SYNDROME SYNDROME TEMPERATURE & PAIN Preserved Abolished Abolished TOUCH Preserved Preserved Preserved VIBRATION & PROPRIOCEPTION Abolished Preserved Preserved DISTRIBUTION Bilateral Bilateral Bilateral 3.5. Brainstem A) Lesions of the Medulla Oblongata B) Lesions of Pons and Midbrain 3.5. Brainstem A) Lesions of the Medulla Oblongata: Cause: lateral medullary infarction due to occlusion of the postero- inferior cerebellar artery (it supplies blood to the lateral medulla)  3.5. Brainstem A) Lesions of the Medulla Oblongata: It affects the trigeminal nerve and the spinothalamic tracts, generally sparing the DCML pathway (as it travels medially) 3.5. Brainstem A) Lesions of the Medulla Oblongata: Clinical features: Impairment of pain and temperature perception Distribution: ipsilateral on the face and contralateral on the body (Harlequin syndrome) Extracted from: Crash Course Neurology  3.5. Brainstem B) Lesions of Pons and Midbrain: A unilateral lesion of the pons or midbrain causes impairment of all sensory modalities on the opposite side of the body (contralateral), as all sensory tracts have already crossed 3.5. Brainstem B) Lesions of Pons and Midbrain: Extracted from: Crash Course Neurology 3.6. Thalamus Thalamic Pain Syndrome: Causes: Stroke Multiple sclerosis Tumours Trauma 3.6. Thalamus Thalamic Pain Syndrome: Clinical features: Impairment of all sensory modalities on the opposite side of the body (contralateral) Hyperpathia Extracted from: Crash Course Neurology  3.7. Somatosensory Cortex A parietal lobe lesion causes: Loss of discriminative sensory function of the opposite side (contralateral) of the face and limbs: impaired two-point discrimination, lack of recognition of objects by touch and loss of proprioception and vibration Pain, temperature and touch are relatively preserved Impaired two-point Impairment of all sensory Impairment of all sensory Impaired pain and temperature: discrimination, proprioception, modalities contralateral to modalities contralateral to ipsilateral to the side of the lesion in and lack of recognition of the side of the lesion; the side of the lesion face; contralateral to the side of the objects by touch contralateral hyperpathia (thalamic pain lesion in limbs (Harlequin syndrome) to the side of the lesion syndrome) Extracted from: Crash Course Neurology