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Disorders of Mental Status

The disorders of mental status include focal syndromes, such as aphasia, apraxia, agnosia, and neglect, followed by more diffuse syndromes, such as delirium and dementia. The aphasias are discussed in Chapter 5.2 . Apraxia: Neurology of Learned Movement Apraxia is a disorder of learned motor acts not caused by paralysis, incoordination, sensory deficit, or lack of understanding of the desired movement. In practical terms, apraxia is…

Multisystem Disorders

Overview For multisystem disorders, the diagnosis often depends on identifying the combination of neurologic and nonneurologic manifestations. For example, neuropathy plus macrocytic anemia should raise concern for B12 or folate deficiency. Confusion, neuropathy, and gastrointestinal (GI) distress might raise concern for lead poisoning. Seizures with fasciculations and profuse salivation suggest cholinesterase toxicity (nerve agent). This section discusses some important multisystem disorders. This is not a complete…

Reflex Abnormalities

Reflex Physiology Reflexes are used for examination purposes, but they demonstrate integral and sometimes complex functioning of the nervous system. Reflexes can be physiologic and pathologic. Physiologic reflexes use pathways that are normally functioning in a patient of the particular age and state. Pathologic reflexes are abnormalities that can be either errors within the reflex pathway or inappropriate responses for the age and state of the…

Gait

Physiology and Localization of Gait The bipedal gait is complex and depends on action of almost all parts of the nervous system. Gait is initiated in different ways depending on the purpose of the movement, whether intentional or reflexive. Gait generally originates in the cerebral cortex. Intentional initiation of gait is influenced by sensory inputs from multiple modalities. The resultant output of the sensory-motor cortex projects…

Coordination

Localization of Coordination Control and Deficits Coordination is a prominent part of the examination. Whereas coordination is typically considered to be a test of cerebellar function, coordination deficits can be produced by a wide range of lesions. Coordination depends on the integrity, not only of the brainstem and cerebellum but also of the sensory and motor afferent and efferent pathways and motor and premotor regions. The…

Sensory

Sensory Systems Localization Two pathways, the dorsal columns and the spinothalamic tract, carry sensory information from the periphery to the brain, and they carry two distinct sets of information. Dorsal Columns The dorsal columns pathway is responsible for fine touch and two-point discrimination, perception of vibration, and conscious proprioception (knowledge of where our joints, limbs, and bodies are in space). Because of its function, it is…

Motor

Motor System Localization Identification and description of motor deficits is critical for the understanding of neurologic localization. The assessment of the presence of weakness and other motor deficits provides an excellent basis for approaching the localization of brain lesions. Elements required for localization of lesions affecting the motor system include: ■ Nature of the deficit ■ Weakness ■ Incoordination ■ Stiffness ■ Tremor ■ Spasms or…

Brainstem and Cranial Nerve Dysfunction

Cranial nerves are discussed elsewhere in this text. This chapter identifies some other commonly seen syndromes involving the brainstem and cranial nerves. Lesions affecting one cranial nerve solely or predominantly are discussed under the respective nerve; brainstem lesions producing cranial nerve dysfunction in addition to other neurologic dysfunctions are discussed individually. Table 4.2.1 summarizes cranial nerve function. Table 4.2.1 Cranial Nerve Function. Number Name Motor Function…

Mental Status

As in every aspect of the neurologic examination, the mental status examination can help to localize a lesion in the nervous system. It can also provide crucial information about the extent and severity of the patient’s deficits. The most important aspect of the mental status examination is the importance of performing it. Some patients maintain a “cocktail party” demeanor of social conversation that can mask major…

Neuromuscular Junction and Muscle

Neuromuscular Transmission Defects Neuromuscular transmission defects present with weakness and fatigability. The tendency to fatigue early and the absence of sensory symptoms are clues to these disorders. These defects are due to impaired synaptic transmission, either from impaired acetylcholine (ACh) release from the presynaptic terminal or reduced available ACh receptors (AChRs) on the postsynaptic terminal. The essential features of the major neuromuscular transmission defects are shown…

Peripheral Nervous System

Approach to Diagnosis Neuromuscular disorders have specific clinical findings, as discussed here, but part of the task of neuromuscular localization is ruling out a lesion of the spinal cord or brain. Central disorders producing peripheral manifestations usually affect systems other than the peripheral nervous system or have an anatomic distribution that would be unusual with a peripheral lesion. For example, weakness in a left median distribution…

Spinal Cord

Spinal Cord Anatomy and Localization Localizing a lesion to a specific location within the cord is key to diagnosis. The differential diagnosis is narrowed by deciding exactly how the cord is affected through the following signs: ■ Corticospinal tract deficits ■ Segmental cord deficits ■ Nerve root deficits Corticospinal tract signs indicate damage to these tracts and include hyperreflexia and abnormal reflexes such as extensor plantar…

Brainstem and Cranial Nerves

Brainstem Dysfunction Midbrain Isolated cranial nerve (CN) III or CN IV palsy is rarely due to a midbrain lesion, despite the location of the nuclei. Midbrain lesions can produce partial or complete palsies of these cranial nerves plus hemiparesis from involvement of the cerebral peduncle or ataxia from damage to the red nucleus. In addition to these direct effects of midbrain lesions, many such lesions can…

Cerebellum

Diagnosis of Cerebellar Lesions The first important distinction in clinical practice is among lesions that primarily affect the vermis, that primarily affect the cerebellar hemispheres, or that diffusely affect the cerebellum. The second important distinction is between lesions that affect only the cerebellum and lesions that affect the brainstem and/or other neural structures. Diagnosis of cerebellar dysfunction depends on history and examination, as with any neurological…

Basal Ganglia and Thalamus

Basal Ganglia Lesions of the basal ganglia typically produce movement disorders, with the predominant results being abnormalities of tone and involuntary movement. For clinical purposes, the important classification is into the following two categories: ■ Akinetic rigid syndromes (too little movement) ■ Involuntary spontaneous movements (too much movement) You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership…

Cerebrum

The uniqueness of the human brain derives from the higher mental functions, such as reasoning, memory, language, speech, calculations, praxis, recognition of objects (gnosis), and the asymmetrical organization of these functions in the cerebral hemispheres. Cerebral dominance, or the specialization of one cerebral hemisphere in specific functions, relates to the unique cytoarchitectural organization of the brain. The cerebral cortex is a large, complex, convoluted structure and…

Peripheral Nerves, Neuromuscular Junction, and Muscle

Anatomy of the Peripheral Neuromuscular System The essential features of the peripheral neuromuscular system are motor nerves, sensory nerves, autonomic nerves, the neuromuscular junction (NMJ), and muscle fibers. Motor neurons originate in the spinal cord and brainstem and innervate skeletal muscle ( Fig. 2.6.1 ). Each motor neuron innervates many muscle fibers, but each muscle fiber is innervated by only one motor neuron. The innervation ratio…

Spinal Cord

Spinal Cord Organization The spinal cord serves as a conduit for information relayed between the brainstem and peripheral nervous system. In addition to this purely conductive function, there is substantial neural processing at segmental levels of the spinal cord. This discussion presumes basic knowledge of spinal cord anatomy and physiology. We review clinically important basic information where it applies to clinical localization and diagnosis. There is…