Differential Diagnosis in Neurology

5.10. Cranial Nerve X

• Anatomy:
  • Dural sheath with XI in the jugular foramen (pars venosum)
  • Inferior to jugular foramen (or within it):
    • Jugular ganglia (general somatic afferent)
    • Nodose ganglia (special and general visceral afferents)
  • Between the two ganglia:
    • Auricular ramus (Nerve of Arnold) branches to innervate the concha of the external ear
    • Meningeal ramus: posterior fossa dura
    • Pharyngeal ramus: forms the pharyngeal plexus with IX; innervates the muscles of the pharynx and soft palate (except stylopharyngeus IX) and tensor veli palatine (V)
    • Superior laryngeal nerve arises from the vagus near the nodose ganglia:
      • External motor branch: cricothyroid muscle
      • Internal ramus: sensory fibers to the larynx
    • Neck: carotid sheath with internal carotid artery and internal jugular vein:
      • Cardiac rami: to the cardiac plexus
      • Recurrent laryngeal nerve:
        • Right side ascends in the tracheoesophageal sulcus
        • Left recurrent laryngeal: beneath the aortic arch to tracheoesophageal sulcus
        • Recurrent laryngeal nerves divide into anterior and posterior rami which supply all muscles to the larynx except cricothyroid
    • Dorsal motor nucleus of the vagus: motor nerves; preganglionic parasympathetic fibers to pharynx, trachea, bronchi, lungs, heart, stomach, small intestine, ascending and transverse colon, liver and pancreas
    • Nucleus ambiguous: all striated musculature of soft palate, pharynx and larynx (except stylopharyngeus IX; tensor veli palatini V
    • Nodose ganglia: taste from epiglottis, hard and soft palate, pharynx, and projects to the nucleus tractus solitarius (NTS)
    • General visceral sensation: oropharynx larynx, lining of thorax and abdominal viscera; cells of origin in the nodose ganglia and project to NTS
    • Exteroceptive sensation from concha: vagus to jugular ganglion to descending tract of V
    • Ipsilateral vocal cord in cadaveric position with Xth nerve lesion (between abduction and adduction)

Lesions of X

• Supranuclear lesion:
  • Cortical representation is at the foot of the precentral gyrus
  • Solitary unilateral palatal weakness with lesion in the corona radiata with no associated limb weakness
  • Bilateral upper motor lesions result in pseudo bulbar palsy
• Pseudo-bulbar palsy:
  • Emotional incontinence
  • Increased gag reflex (rarely decreased)
  • Dysphagia
  • Pathologic laughter and crying
  • Spastic tongue
  • Explosive spastic dysarthria
  • Gag reflex: may be associated with retching and vomiting
  • Associated extremity spasticity
• Medullary lesions:
  • Wallenberg's
  • Syringobulbia
  • Motor neuron disease
  • Inflammatory disease (demyelinating)
  • Primary and metastatic tumors
• Rostral part of the nucleus ambiguous injured:
  • Palatal pharyngeal paralysis of Avellis
  • Larynx spared
• Posterior fossa lesions affecting X:
  • Glomus jugulare tumor
  • Metastatic disease
  • Meningioma
  • Chordoma
• Miscellaneous:
  • Carcinomatosis of the meninges
  • Idiopathic pachymeningitis
  • Leukemia/lymphoma
  • Sarcoidosis
  • AIDP
  • Trauma
  • EBV
  • CMT-4C

Syndromes

• Jugular foramen: (Vernet) IX, X, XI
• Schmidt: X, XI (venous component)
• Hughlings' Jackson: X, XI, XII
• Collet–Sicard: IX, X, XI, XII
• Vagal nerve lesions (trunk):
  • Neck or thorax
  • Ipsilateral vocal cord paralysis; unilateral laryngeal anesthesia
  • Differential diagnosis:
    • Tumor (lung most common)
    • Aneurysm internal carotid artery
    • Trauma
    • Enlarged lymph node
• Superior laryngeal nerve:
  • Primarily a sensory branch; cricothyroid muscle weakness with minimal hoarseness and hypophonia
  • Surgery, trauma, tumor
• Recurrent laryngeal nerve:
  • Left damage > right (longer nerve)
  • Unilateral paralysis:
    • Transient hoarseness
    • Flaccid dysphonia: harshness and breathiness, decreased volume, mid inhalation stridor
    • Palate pharyngeal function normal
    • Diplophonia: two pitch levels produced by unequal frequency of vibration between the two vocal cords
    • Semon's law:
      • Abductor muscles of larynx affected first with peripheral nerve injury
  • Differential diagnosis:
    • 25% cause unknown
    • Aneurysms of aortic arch or subclavian artery
    • Enlarged tracheobronchial lymph nodes
    • Mediastinal tumor
    • Thyroidectomy
    • Cancer extending behind the carotid sheath at C6 level: combination of recurrent laryngeal, phrenic, vagal, preganglionic sympathetic (Rowland-Payne Syndrome)
• Bilateral recurrent laryngeal nerve:
  • Thyroidectomy
  • Carcinoma of thyroid
  • Carcinoma of esophagus
  • AIDP (descending form)
  • Bilateral abductor paralysis (cord lies midline or near midline):
    • Approximation of the vocal cords
    • Weak voice that is clear
    • Inspiratory stridor
    • Dyspnea on exertion
• Bilateral lesions affecting the superior laryngeal nerve:
  • Damage above the nodose ganglion
  • Associated palatal and pharyngeal paralysis
  • Vocal cords in the cadaveric position
  • Phonation severely compromised
  • Vocal pitch cannot be changed

Vagal Autonomic Functional Deficits

• Esophageal, gastric and intestinal motility:
  • Esophageal motility:
    • With denervation hypersensitivity to cholinomimetic drugs; primary action at the smooth muscle in the lower third of the esophagus
    • Achalasia: cholinergic medicines cause uncoordinated and painful contraction of the esophagus
  • Gastric mobility:
    • Gastroparesis (diabetes, amyloid)
    • Hyperactivity (gastrojejunostomy and pyloroplasty; increased gastric emptying may cause early dumping syndrome (postprandial weakness, light headedness, flushing, sweating, palpitations, tachycardia); later dumping syndrome (insulin release with sugar ingestion; reactive hypoglycemia; diarrhea may be associated)
  • Intestinal motility:
    • Measured by evaluation of myenteric migrating complexes (MMC's)
    • Absent MMC: neuropathy or intestinal muscle impairment
  • Pancreatic polypeptide release (depends on the vagus):
    • Increased levels with hypoglycemia
    • Measure of abdominal vagal activity
    • Autonomic failure with vagal denervation (diminished levels of pancreatic polypeptides with hypoglycemia occur)
    • Vagovagal syncope increases pancreatic peptide levels

Vagal Efferent Dysfunction

• Cardiac:
  • Neural control of heart rate is primarily vagal
  • Blocked vagus: heart rate 100–110 beats per minute
  • Diminished cardiac vagal tone:
    • Multiple system atrophy; degeneration of the vagal nuclei
    • Primary autonomic failure; peripheral vagal nerve degeneration
    • Diabetic autonomic failure; heart rate is initially high and then falls
  • Chronic autonomic failure:
    • Decreased HR response to hyperventilation
    • Similar response in polyneuropathies and autonomic failure secondary to alcohol
  • Vagal dysfunction earlier than sympathetic loss:
    • Alcoholism
    • Non-alcoholic liver disease
    • Cardiac transplantees'
    • Ocular hypertension
    • Severe obesity
• Impaired vagal innervation of the GI tract:
  • Primary autonomic failure:
    • Decreased gastric emptying
    • Impaired pancreatic polypeptide response to hypoglycemia
  • Diabetic neuropathy:
    • Peripheral vagal degeneration
    • Gastric dilation with reduced peristalsis and delayed emptying
    • Nocturnal watery diarrhea
  • Gastrointestinal atrophy with botulism
  • Pure cholinergic dysautonomia (putative immune basis)
  • Destruction of intrinsic gut plexuses:
    • Achalasia (esophageal sphincter degenerates and fails to relax)
    • Chagas disease (cellular immune response: anti-parasympathetic neuronal IgG)
• Vagal nerve hyperactivity:
  • Emotional syncope (vagovagal):
    • Sight or thought of specific stimulus
    • Brachycardia
    • Loss of consciousness
  • Oculocardiac reflex
  • Vagal reflexes augmented by drugs and anesthetics
  • Glossopharyngeal neuralgia (some sensory radiations into X territory)
  • Swallow syncope (Charcot's)
  • Carotid sinus hypersensitivity
  • Plural aspiration
  • Increased vagal activity with high cervical cord lesions:
    • Hypoxia
    • Pulmonary emboli
    • Acidemia
    • Decreased cardiac sympathetic tone (cord lesion)
    • Paralysis of respiration (decreased activation of the pulmonary stretch reflex which inhibits the vagus)
    • Tracheal intubation in quadriplegics
    • Volatile substance abuse (enhances vagal activity)
    • Hyperactive diving reflex

Aberrant Regeneration of IX and X

• Gustatory sweating:
  • Excessive sweating during eating
  • Damage to lesser superficial petrosal nerve (aberrant postganglionic sympathetic nerves in auriculotemporal distribution; Frey's syndrome)
  • May occur with: neck operations, thoracotomy or T2 sympathetectomy
  • Gustatory piloerection may be associated with sweating; aberrant innervation of the sympathetic ganglia
  • Gustatory sweating in diabetics in the territory of the superior cervical ganglia

Vagal Afferent Dysfunction

• Cough Reflex:
  • Supplies sensation to the mucous membrane of the larynx and the tracheobronchial tree
  • Afferent limb of the cough reflex
  • Bilateral lesions cause aspiration
  • Stimulation of trachea and larynx in tetanus causes severe hypertension (sympathetic overactivity; hypotension and bradycardia in tetraplegics)
• Superior laryngeal neuralgia:
  • Paroxysmal lancinating pain
  • Radiation from the side of the thyroid cartilage to the angle of the jaw; occasionally to the ear
  • Trigger: pressure over the skin that overlies the thyrohyoid membrane
• Pulmonary Vagal Afferents:
  • Pulmonary stretch receptors increase activity with inspiration
  • Receptors in the chest wall for stretch are more active than pulmonary afferents
  • Vagal lung irritant receptors: respond to irritants, over or underinflation, emboli or congestion (neuropeptide P mediated)
• Cardiac Receptors:
  • Activation of cardiac vagal afferents in the ventricle substance P (SP) mechanoreceptors: induce bradycardia, hypotension and syncope
  • Stimulated by forceful contraction:
    • Aortic stenosis
    • Tilt table
    • Coronary arteriography (bradycardia and hypotension)

Vascular Lesions Affecting the Xth Nerve

• Wallenberg's syndrome (N ambiguous)
• Hemorrhage: hypertension (rare <1%); cavernous hemangioma; AVM; telangiectasias of the medulla
• Aortic arch aneurysm (recurrent laryngeal)
• Dissection of the internal carotid artery
• Left atrial distention (mitral stenosis)

Autoimmune Processes

• AIDP
• Putative "idiopathic" form
• Occasionally with neuralgia amyotrophica
• Sarcoid
• MG
• Cholinergic dysautonomia

Neuropathy

• Neuritic Beriberi
• Sjögren's syndrome
• AIDP
• Alcohol
• Drug induced SLE (bilateral)
• HSMN-type II (vocal cord involvement); CMT-4C
• Vincristine
• Idiopathic pachymeningitis (compression)

Syndromes Affecting the X Nerve

• Wolfram (adductor spasm)
• Sjögren's
• Tapia (ipsilateral tongue and vocal cord)
• Vernet's (IX, X, XI) jugular foramen
• Collet-Sicard (IX, X, XI, XII)
• Schmidt's (X, XI)
• Hughlings Jackson (X, XI, XII)
• Shy Drager:
  • Cricoarytenoid (recurrent laryngeal nerve)
  • Upper airway dysfunction
  • Central respiratory dysfunction
  • Sudden death during sleep
• Issa's syndrome of the larynx
• Idiopathic adductor spasm (spastic dysphonia)
• Arnold–Chiari (type I)
• Laryngeal nerve neuralgia
• Swallow syncope (Charcot's syncope)

Trauma

• Insertion of nasogastric or endotracheal tube:
  • Injures the posterior branch of the recurrent laryngeal nerve
  • Posterior cricoarytenoid muscle and interarytenoid muscles affected
  • The nerve is damaged behind the thyroid cartilage
• Bilateral laryngeal nerve injury (thyroidectomy)
• Injury to recurrent laryngeal nerve:
  • Distention of the esophagus (achalasia may be bilateral and reversible)
  • Delayed post-operative palsy (edema)
• Severe neck trauma
• Pharyngeal plexus (terminal branches of IX and X); flexion-extension neck injury; surgery (tonsillectomy)

Tumors of the Xth Nerve

• Schwannoma
• Chemodectoma
• Chordoma/meningioma (jugular foramen)
• Carcinomatosis of the meninges
• Metastatic lung; breast; thyroid
• Recurrent laryngeal nerve:
  • Malignant mediastinal tumors
  • Esophageal cancer
  • Mediastinal tumors
  • Lymphoma
  • Thyroid

Idiopathic Xth Nerve Palsy

• Males 2× > females
• 3rd decade of life
• Perhaps 20% of Xth nerve lesions
• Left side more frequently affected than the right
• Unilateral recurrent laryngeal nerve palsy:
  • Twice as common as that seen in combination with superior laryngeal nerve
  • DM
  • Idiopathic
  • Infection