Neurotransmitter-based diagnosis and treatment: A hypothesis (Part 3)

Glutamate excess (Table 2^9,18-30)

Mr. B is anxious and bites his fingernails and cheek while you interview him.¹⁸ He has scars on his lower arms that were caused by years of picking his skin.¹⁸ He complains of headache^28-30 and deep muscle, whole body,^19-23 and abdominal pain.²⁰ Both hyperesthesia (he calls it “fibromyalgia”)^9,19,20,22 and irritable bowel syndrome flare up if he eats Chinese food that contains monosodium glutamate.²¹ This also increases nausea, vomiting, and hypertensive episodes.^{9,19,20,22,24,26} Mr. B developed and received treatment for opioid use disorder after being prescribed morphine for the treatment of fibromyalgia.²² He is being treated for posttraumatic stress disorder at the VA hospital and is bitter that his flashbacks are not controlled.²³ Once, he experienced a frank psychosis.²⁶ He commonly experiences dissociative symptoms and suicidality.^23,26 The sensations of crawling skin,¹⁸ panic attacks, and nightmares complicate his life.²³ Mr. B is angry that his “incompetent” psychiatrist stopped his diazepam and that it “almost killed him” by causing delirium.²⁴ He suffers from severe neuropathic pain in his feet and says that his pain, depression, and anxiety respond especially well to ketamine treatment.^9,23,26 He is prone to euphoria and has had several manic episodes.²⁶ In childhood, his parents brought him to a psychiatrist to address episodes of head-banging and self-hitting.¹⁸ Mr. B developed seizures; presently, they are controlled, but he remains chronically dizzy.^9,24,25,27 He claims that his headaches and migraines respond only to methadone and that sumatriptan makes them worse, especially in prolonged treatment.^28-30 He is tachycardic, tremulous, and makes you feel deeply uneasy.^9,24

Impression. Mr. B has many symptoms of glutamate hyperactivity. The use of N-methyl-D-aspartate receptor antagonists such as memantine and dextromethorphan and alpha-blockers (eg, clonidine and tizanidine) may be considered. Avoiding addictive substances would be prudent, though the use of ketamine seems rational. Anticonvulsants are recommended, along with sedating antidepressants. Serotonin-norepinephrine reuptake inhibitors may not be the best choice because norepinephrine potentiates glutamate function. Dopamine inhibits glutamate, so stimulants, bupropion, and amantadine³¹ may be paradoxically applied to treatment of both cognitive and physical symptoms (including pain) in a patient with glutamate hyperactivity.

Glutamate deficiency (Table 2^9,32-38)

Mr. Z feels dull, fatigued, and unhappy.^32,33,37 He is overweight and moves slowly. Sometimes he is so slow and clumsy that he seems obtunded.^9,36,37 He states that his peripheral neuropathy does not cause him pain, though his neurodiagnostic results are unfavorable.³² Mr. Z’s overall pain threshold is high, and he is unhappy with people who complain about pain because “who cares?”³² His memory and concentration were never good.^33,37,38 He suffers from insomnia and is frequently miserable and disheartened.^32,33,38 People view him as melancholic.^33,37 Mr. Z is mildly depressed, but he experiences aggressive outbursts^37,38 and bouts of anxiety,^32,33,36,38 psychosis, and mania.^33,37,38 He is visibly confused³⁷ and says it is easy for him to get disoriented and lost.^37,38 His medical history includes long-term constipation and several episodes of ileus.^9,34,35 His childhood-onset seizures are controlled presently.³³ He complains of frequent bouts of dizziness and headache.^32,34,35 On physical exam, Mr. Z has dry mouth, hypotension, diminished deep tendon reflexes, and bradycardia.^9,34,35 He sought a consultation from an ophthalmologist to evaluate an eye movement problem.^33,36 No cause was found, but the ophthalmologist thought this problem might have the same underlying mechanism as his dysarthria.³³ Mr. Z’s balance is bothersome, but his podiatrist was unable to help him to correct his abnormal gait.^33-36 A friend who came with Mr. Z mentioned she had noticed personality changes in him over the last several months.³⁷

Impression. Mr. Z exhibits multiple signs of low glutamatergic function. Amino acid taurine has been shown in rodents to increase brain levels of both GABA and glutamate. Glutamate is metabolized into GABA, so low glutamate and low GABA symptoms overlap. Glutamine, which is present in meat, fish, eggs, dairy, wheat, and some vegetables, is converted in the body into glutamate and may be considered for a patient with low glutamate function. The medication approach to such a patient would be similar to the treatment of a low GABA patient and includes glutamate-enhancing magnesium and dextromethorphan.

Rarely is just 1 neurotransmitter involved

Most real-world patients have mixed presentations with more than 1 neurotransmitter implicated in the pathology of their symptoms. A clinician’s ability to dissect the clinical picture and select an appropriate treatment must be based on history and observed behavior because no lab results or reliable tests are presently available.

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