Disorders

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© Springer Nature Switzerland AG 2021

R. Reti, D. Findlay (eds.)Oral Board Review for Oral and Maxillofacial Surgerydoi.org/10.1007/978-3-030-48880-2_19

19. Neurological Disorders

Simon Bangiyev1  , David Chang2, David E. Urbanek3, Raymond Charles DickeyJr4, Robert Reti5 and Damian Findlay6
(1)

Yale New Haven Hospital, Oral and Maxillofacial Surgery, New Haven, NY, USA
(2)

Tufts University School of Dental Medicine Oral and Maxillofacial Surgery, Tufts Medical Center, Oral and Maxillofacial Surgery, Boston, MA, USA
(3)

Missouri School of Dentistry and Oral Health, Mercy Hospital, St. Louis MO, Department of Oral and Maxillofacial Surgery, Chesterfield, MO, USA
(4)

Mercy Hospital, Oral Facial Surgery Institute, St. Louis, MO, USA
(5)

Southwest Oral Surgery, St. Louis, MO, USA
(6)

Oral Facial Surgery Institute, St. Louis, MO, USA
 
Keywords

Amyotrophic lateral sclerosis (ALS)Parkinson diseaseCerebrovascular accidentAlzheimer’s diseaseSeizure disorderStatus epilepticusMultiple sclerosis (MS)Spinal cord injury

Amyotrophic Lateral Sclerosis (ALS)

  • ALS is a progressive neurodegenerative disease of the upper and lower motor neurons due to degeneration of lateral corticospinal tracts, which will eventually lead to muscle failure.

  • Commonly affects men between the ages of 40 and 60.

  • Also known as Lou Gehrig’s disease.

  • Presents with progressive muscle weakness, hyperreflexia (due to upper motor neuron involvement), muscle fasciculations (due to lower motor neuron involvement), and atrophy.

  • Maxillofacial implications – dysphagia due to pharyngeal muscle weakness leading to an aspiration risk (bulbar nuclei involvement), tongue weakness with fasciculations, and sialorrhea due to inability to handle secretions.

  • Death is usually due to respiratory complications (aspiration, inadequate ventilation due to diaphragm, and accessory muscle weakness). Patients also have an inadequate cough reflex.

Treatment

  • No curative treatment.

  • The drug riluzole, a glutamate blocker, may provide neuroprotection and extend survival.

  • Supportive treatments include antibiotic prophylaxis for aspiration, gastrostomy, tracheostomy, and mechanical ventilation.

Patient Management

  • Consult the patient’s physician to ascertain baseline respiratory status.

  • Consider treatment in the operating room for airway management. Increased risk of aspiration due to bulbar involvement, respiratory weakness, and sialorrhea. Consider anticholinergic preoperatively.

  • Succinylcholine may cause hyperkalemia secondary to denervation and immobilization.

  • General anesthetics may lead to prolonged respiratory depression.

  • Nondepolarizing blockade may lead to prolonged neuromuscular blockade.

  • Patients prone to autonomic dysfunction, which manifests as tachycardia and orthostatic hypotension.

  • Avoid regional anesthesia as it may exacerbate disease.

Alzheimer’s Disease

  • Alzheimer’s disease (AD) is a neurodegenerative disease characterized by the progressive loss of cortical neurons and the formation of amyloid plaques and intraneuronal neurofibrillary tangles.

  • The progressive loss of neurons eventually leads to a relative deficiency in cortical acetylcholine transmission (resulting from loss of neurons in the nucleus basalis).

  • AD is the most common neurodegenerative disease and the most common cause of dementia in persons older than 65 years of age.

  • Patients with AD show a slow, progressive decline in intellectual function. Hallmarks of the disease include impaired memory, judgment, and decision-making, and emotional lability. Extrapyramidal signs, apraxias, and aphasias are present late in the course of the disease.

  • Classification – AD is categorized into two forms (with continued further research, it is very likely that AD will continue to be subcategorized into more precise etiological categories):

    1. 1.
      Familial form (early-onset AD)

      • Rare.

      • Early onset, usually before age 60.

      • Autosomal dominant pattern of inheritance.

      • Is almost universal in older patients with Down syndrome (trisomy 21).

       
    2. 2.
      Sporadic form

      • More common.

      • Typically occurs after 60 years of age.

       

Workup and Diagnosis

  • The clinical diagnosis of AD is by exclusion.

  • Definitive diagnosis is usually made on postmortem examination via autopsy (presence of accumulation of amyloid plaques and neurofibrillary tangles).

  • MRI imaging is preferred in diagnosis of AD. Will demonstrate marked cortical atrophy with ventricular enlargement.

Treatment

  • There is no cure for AD and treatment focuses on control of symptoms. Even with treatment, prognosis is poor.

  • The pharmacological agents for AD include cholinesterase inhibitors (tacrine, donepezil, rivastigmine, and galantamine), and the glutamate antagonist, memantine.

  • Antipsychotics, antidepressants, and anxiolytics may be useful for patients with behavioral disturbances.

Patient Management

  • Patients with AD are often confused and can be uncooperative. While some patients may tolerate a procedure with local anesthesia, many may need some sort of procedural sedation.

  • Inquire who makes health care decisions for the patient if the patient does not possess capacity (power of attorney/health care advocate).

  • As a general rule, anesthetic dosages should be decreased due to increased sensitivity and decreased pharmacokinetics resulting in a slower distribution and reduction in clearance [1].

  • As a general rule, doses of sedative-hypnotics should be reduced by 30% [1].

  • Preferred medications include short-acting sedative-hypnotics, anesthetic agents, and narcotics since they allow a more rapid recovery.

  • Patients are at a higher risk of delirium and postoperative cognitive dysfunction after an anesthetic challenge [1].

  • Centrally acting anticholinergics, such as atropine and scopolamine, may contribute to postoperative cognitive dysfunction and should be avoided if possible.

  • Glycopyrrolate, which does not cross the blood–brain barrier, is the preferred agent when an anticholinergic is needed.

  • Have the patient continue their AD medications preoperatively.

Parkinson’s Disease

  • Parkinson’s disease (PD) is a neurodegenerative disease characterized by the classic triad of bradykinesia, rigidity, and resting (pill-rolling) tremor.

  • It is caused by the progressive loss of dopaminergic neurons in the pars compacta of the substantia nigra in the basal ganglia.

  • The depletion of dopamine results in the diminished inhibition of neurons in the extrapyramidal motor system and unopposed stimulation by acetylcholine, thereby producing the tremor of Parkinsonism.

  • PD typically affects individuals older than 60 years of age.

  • Other signs include postural instability, bradyphrenia (slowness of thought processes), akinesia (lack of spontaneous movement), and problems with walking.

  • Patients note unilateral symptoms initially, which subsequently spread to involve both sides.

  • Tremors – are rhythmic, alternating flexion and extension of the thumbs and other digits. They are typically described as “pill-rolling tremors.” Tremors are more prominent at rest and tend to disappear during voluntary movement.

  • Rigidity – first presents in the proximal muscles of the neck but may progress to absence of head rotation when turning the body and loss of arm swings when walking.

  • Akinesia – facial immobility presenting as infrequent blinking and paucity of facial expression.

Workup and Diagnosis

  • The diagnosis of PD is made according to the clinical signs of tremor, bradykinesia, muscular rigidity, and postural instability.

  • Neuroimaging of no value.

  • Dopaminergic challenge (administration of levodopa) provides clinical support for diagnosis if improvement demonstrated.

Treatment

  • The goal is to increase the concentration of dopamine in the basal ganglia.

  • Carbidopa-levodopa (Sinemet®) is the mainstay of treatment of PD. Levodopa is a dopamine precursor that is combined with the decarboxylase inhibitor, carbidopa, which prevents peripheral conversion of levodopa to dopamine, thereby optimizing the amount of levodopa that can enter the CNS. Carbidopa-levodopa can also be combined with the catechol-O-methyltransferase (COMT), entacapone (the three-drug combination marketed as Stalevo®), which blocks the peripheral breakdown of levodopa and, therefore, maximizes the amount of levodopa that can cross the blood-brain barrier.

  • Selegiline and rasagiline are type B monoamine oxidase (MAO-B) inhibitors that help control PD symptoms by inhibiting the catabolism of dopamine in the CNS. They are used in patients with early PD and delay the need for levodopa treatment. Anticholinergics and antihistamines are also used to antagonize the effects of acetylcholine.

  • Surgical treatment – patients who fail medical treatment are candidates for surgical intervention (such as thalamotomy, pallidotomy, or implantation of a deep brain stimulator).

Patient Management

  • Have the patient continue their medications preoperatively. The half-life of levodopa is short and abrupt withdrawal can cause worsening of muscle rigidity and interfere with ventilation.

  • Nausea/vomiting are side effects of levodopa and may be treated with ondansetron, dexamethasone, and transdermal scopolamine.

  • Avoid phenothiazines (promethazine), butyrophenones (droperidol), and metoclopramide because their antidopaminergic activity can exacerbate symptoms.

  • Diphenhydramine may be used for patients with tremor.

  • Propofol is relatively safe and may have some antiparkinsonian effects via GABAergic and glutamate transmission [2].

  • Opioids should be used judiciously as patients with PD have a higher incidence of chest wall rigidity [2]. If a patient is treated with monoamine oxidase inhibitors (MAOI), reduction in opioid dosage is advised due to decrease in liver metabolism of narcotics.

  • Be mindful of serotonin syndrome risk on patients taking MAOI (hypertension, tachycardia, hyperthermia, diaphoresis, confusion and agitation).

  • The chronic administration of levodopa may result in depletion of norepinephrine stores in the autonomic nervous system, which may sensitize adrenergic receptors to epinephrine administered with local anesthetic cartridges, and result in elevated blood pressure. Ketamine may be relatively contraindicated because of this and should be used judiciously.

  • Many patients with PD have baseline autonomic dysfunction which can manifest as orthostatic hypotension, labile blood pressures, and sialorrhea [2].

  • Monitor arterial blood pressure carefully. Hypotension should be treated with fluids and small doses of phenylephrine (a direct-acting vasopressor), rather than ephedrine.

  • Inhalational anesthetics decreases dopaminergic transmission and may exacerbate symptoms [2].

Multiple Sclerosis

  • Multiple sclerosis (MS), an inflammatory demyelinating disease of the central nervous system (CNS), is marked by discrete episodes of neurological dysfunction, termed relapses, followed by periods of remission.

  • Such a course is termed relapsing-remitting and occurs in about 82% of patients. The remaining patients (18%) have a primary progressive course without discrete relapses. Many patients with relapsing-remitting MS eventually advance to a steady irreversible progression termed secondary progressive MS [1].

  • The cause remains unknown; however, evidence suggests that MS is an autoimmune disease triggered by unknown environmental factors.

  • Affects women more frequently than males (2:1).

  • Onset commonly occurs between the ages of 20 and 40 years [1].

  • Pathogenesis – demyelination preferentially occurs in the periventricular areas of the brain, due to autoimmune processes involving T and B autoreactive cells.

  • Symptoms – based on multifocal involvement (reflects sites of demyelination). May manifest as visual disturbances, gait disturbances, ascending paresis, limb paresthesias. MS may present as bilateral trigeminal neuralgia.

Workup and Diagnosis

  • MRI with gadolinium is the best study to demonstrate demyelination in the CNS due to its ability to delineate between normal myelin and MS lesions.

  • CSF analysis will typically show increased intrathecal synthesis of immunoglobulin G (IgG). Isoelectric focusing gel of CSF will show oligoclonal banding of IgG.

  • Evoked potential testing measures electrical activity in parts of the CNS caused by light, sound and touch. A patient with MS will have reduced neurotransmision from stimuli. Visual evoked potential is the most commonly used as it is the most sensitive of the evoked potentials studies to diagnose MS. Brain stem and somatosensory evoked potentials can also be utilized.

Treatment

  • Treatment of MS consists of management of acute relapses aimed at reduction of the severity and frequency of these relapses, and slowing the progression of the disease.

  • Treatment of major relapses is with IV methylprednisolone (500–1000 mg daily for 3–5 days), and sometimes followed by a taper of oral prednisone.

  • Other therapies include treatment with interferon-B, glatiramer acetate, natalizumab, mitoxantrone, and plasmapheresis.

  • There is no cure for MS.

Patient Management

  • Surgical stresses are associated with exacerbation of symptoms [3]. Provide adequate anxiolysis and pain management to avoid exacerbations.

  • Elective surgery should be avoided during periods of relapse, regardless of the anesthetic technique used.

  • The informed consent discussion should include the possibility of worsening MS symptoms.

  • Avoid increases in body temperature, which will lead to an exacerbation of symptoms.

  • Consider stress-dosing the patient who is on long-term steroids.

  • Patients taking interferon should have a CBC to exclude anemia, neutropenia, and thrombocytopenia.

  • There are no recognized interactions with general anesthetics in patients with MS.

  • Patients with advanced disease may have a labile cardiovascular system due to autonomic dysfunction. Be prepared to treat labile blood pressures and heart rates.

  • A patient’s ability to cough, exhale deeply, or clear secretions may be impaired and put them at risk for aspiration.

  • Avoid succinylcholine in patients with paralysis or paresis because of the potential for hyperkalemia.

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Jul 23, 2021 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Disorders
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