Syndromes of Lesion of Sensory Systemon Different LevelsPeripheral Nerve Lesions
Mononeuropathy. A mononeuropathy is a lesion of one nerve by a local process, usually compression, trauma or a vascular cause. Clinical examination typically demonstrates negative and positive sensory disturbances restricted to the territory of the nerve involved.
Polyneuropathy. In patients with polyneuropathies, sensory loss is symmetric and more frequently distally than proximally (stocking-and-glove sensory loss). The peripheral nervous system is involved diffusely. Sensory loss may be accompanied by a motor deficit.
Plexus lesion. It is appeared by hypo- or anesthesia of all sorts of sensation in the region of plexal innervation with pain, paresthesias and vegetative disorders
Root lesion. Pain due to root compression is generally accompanied by sensory loss in appropriate dermatom, muscle weakness, and decreased or absent tendon reflexes. If the spinal ganglion is involved, the herpes zoster is appeared.
Cord lesion. In patients with a cord lesion, there may be a transverse sensory level. Physiologic areas of increased sensitivity do occur, however, at the costal margin, over the breasts, and in the groin, and these must not be taken as abnormal. Therefore, the level of a sensory deficit affecting the trunk is best determined by careful sensory testing over the back rather than the chest and abdomen.
Central cord lesion. Central cord lesion (such as syringomyelia, following trauma, certain cord tumors) may cause a loss of pain and temperature appreciation with sparing of other modalities. This loss is due to the interruption of fibers conveying pain and temperature that cross from one side of the cord to the spinothalamic tract on the other. Such a loss is usually bilateral, may be asymmetric. It may be accompanied by lower motor neuron weakness in the muscles supplied by the affected segments.
The level of the posterior horn. Disorders in the posterior horn are characterized by pain and temperature sensivity disorders.
Anterolateral cord lesion. Lesions involving the anterolateral portion of the spinal cord (lateral spinothalamic tract) can cause contralateral abnormality of pain and temperature sensation in segments below the level of the lesion.
Anterior grey commissure. Lesion in its region cause dissociated disorders – pain and temperature sensations disorders in symmetrical parts of body like a “butterfly” or “jacket”.
Anterior cord lesion. With destructive lesions involving the anterior portion of the spinal cord, pain and temperature appreciation are impaired below the level of the lesion from lateral spinothalamic tract involvement. Weakness or paralysis of muscles supplied by the involved segments of the cord results from damage to motor neurons in the anterior horn.
Posterior column lesion. There is loss of vibration and joint position sense below the level of the lesion, with preservation of other sensory modalities.
Cord hemisection. Lateral hemisection of the cord leads to Brown-Sequard's syndrome. Below the lesion, there is an ipsilateral pyramidal deficit and disturbed appreciation of vibration and joint position sense, with contralateral loss of pain and temperature appreciation that begins two or three segments below the lesion.
Brainstem lesion. Sensory disturbances may be accompanied by a motor deficit, cerebellar signs, and cranial nerve palsies when the lesion is in the brainstem. In patients with lesions involving the spinothalamic tract in the dorsolateral medulla and pons, pain and temperature appreciation are lost in the limbs and trunk on the opposite side of the body. When such a lesion is located in the medulla, it also typically involves the spinal trigeminal nucleus, impairing pain and temperature sensation on the same side of the face as the lesion. The result is a crossed sensory deficit that affects the ipsilateral face and contralateral limbs. In contrast, spinothalamic lesions above the spinal trigeminal nucleus affect the face, limbs, and trunk contralateral to the lesion. With lesions affecting the medial lemniscus, there is loss of touch and proprioception on the opposite side of the body. In the upper brainstem, the spinothalamic tract and medial lemniscus run together so that a single lesion may cause loss of all superficial and deep sensation over the contralateral side of the body.
Medial lemniscus lesion cause hemianesthesia and sensitive hemiataxia (anesthesia of deep sorts of sensation).
Thalamic Lesions. Thalamic lesions may lead to loss or abnormality of all forms of sensation on the contralateral side of the body and is appeared by hemianesthesia, sensitive ataxia, hemianopsia, hemialgia. Spontaneous pain, hyperpathia may occur on the affected side. Patients may describe it as burning, tearing, knifelike, or stabbing. Any form of cutaneous stimulation can lead to painful or unpleasant sensations. Some later develop persistent severe pain and choreoathetoid movements on the affected side, mild hemiataxia, and astereognosis. Called also Dejerine-Roussy syndrome.
Lesion of internal capsule. Involvement of the sensory radiations in the internal capsule causes variable and sometimes extensive diminution of all types of sensation on the opposite side of the body. The changes are similar to those which follow a thalamic lesion, and it may be difficult to differentiate between the two. Pain, however, is rarely experienced. There are hemianesthesia, hemiataxia, hemiplegia.
Lesions of the sensory cortex (postcentral gyrus). Cortical sensory disturbances are usually appeared by monoanesthesia in the opposite side of body. Stimulation of postcentral gyrus cause sensitive "Jackson"-the feeling of tingling or numbness in the opposite side. Lesion of upper parietal lobule is characterized by astereognosis.