Nystagmus + Hyperemesis Gravidarum in First Trimester → Wernicke Encephalopathy

Diagnosis

1. Nystagmus (and other ocular signs — abducens/conjugate gaze palsies)
2. Ataxia of gait
3. Confusion/global confusional state

"Wernicke disease is characterized by nystagmus, abducens and conjugate gaze palsies, ataxia of gait, and confusion. These symptoms develop acutely or subacutely and usually occur in varying combinations." — Adams and Victor's Principles of Neurology, 12th ed.

Pathophysiology

• Severe caloric restriction → relative thiamine depletion
• Thiamine stores are exhausted in 7–8 weeks of inadequate intake
• Concurrent IV glucose administration (without thiamine) dramatically accelerates depletion — glucose metabolism demands thiamine as a cofactor for pyruvate dehydrogenase and α-ketoglutarate dehydrogenase

Neurological Findings in HG-Associated Wernicke's

"Signs of peripheral nerve involvement may be found in patients with hyperemesis gravidarum who have Wernicke encephalopathy. In the limbs, numbness, paresthesias, and dysesthesias are accompanied by cutaneous sensory loss..." — Creasy & Resnik's Maternal-Fetal Medicine

Imaging

• FLAIR and T2: Symmetric hyperintensities around the periaqueductal grey, tectal plates, medial thalami, and bilateral mammillary bodies
• DWI may show restricted diffusion in acute necrosis
• Contrast enhancement may be present
• Late finding: shrunken mammillary bodies

CT is far less sensitive and should not be used to exclude the diagnosis.

Laboratory

• ↓ Serum thiamine level
• ↓ Erythrocyte transketolase activity
• ↑ Serum pyruvate
• Hypokalemia, metabolic alkalosis (from vomiting)
• Ketonuria, elevated urine specific gravity

Do NOT wait for lab confirmation before treating — treatment must be immediate upon clinical suspicion.

Treatment — A Medical Emergency

⚠️ Critical rule: Give thiamine BEFORE glucose

Thiamine Dosing

"Patients suspected of having the disorder should receive thiamine before administration of glucose to avoid precipitation of symptom worsening. A dose of 500 mg should be given IV in the acute stage, followed by 100 mg 3 times daily during the first week." — Bradley and Daroff's Neurology in Clinical Practice

"Certain writings indicate that initial doses of 500 mg are necessary to fully reverse the manifestations of Wernicke disease and prevent progression to Korsakoff syndrome." — Adams and Victor's Principles of Neurology

Additional measures

• Magnesium supplementation (required cofactor for thiamine activity)
• IV fluid rehydration (Ringer's lactate)
• Parenteral antiemetics (ondansetron 4 mg IV q8h; use after 10 weeks if possible given teratogenicity concerns)
• Correct electrolytes (especially potassium)
• Full B-vitamin replacement (patients are often deficient in multiple B vitamins)
• Admission for monitoring; consider enteral/parenteral nutrition if HG is refractory

Prognosis

• Ocular signs (including nystagmus) resolve within hours of thiamine administration — the most rapidly reversible feature
• Fine horizontal nystagmus may persist in ~60% of patients
• Gait disturbance resolves slowly; over one-third have abnormal gait even months after treatment
• If untreated → Korsakoff syndrome (irreversible anterograde amnesia + confabulation) — fewer than 20% with Korsakoff syndrome fully recover
• Mortality 10–20% even with treatment in early studies

Key Teaching Points

1. Nystagmus in a pregnant patient with HG = Wernicke's until proven otherwise
2. The complete triad (nystagmus + ataxia + confusion) is present in only a minority — diagnose on clinical suspicion
3. Never give glucose before thiamine in any malnourished/vomiting patient
4. High-dose IV thiamine (500 mg) is safe in pregnancy
5. Thiamine prophylaxis (100 mg PO/IV daily) should be given to all patients with prolonged HG requiring IV fluids — Yamada's Textbook of Gastroenterology
6. Risk to fetus: thiamine and vitamin K deficiency also cause fetal complications (bleeding diatheses)

• Adams and Victor's Principles of Neurology, 12th ed., Wernicke-Korsakoff Syndrome chapter
• Bradley and Daroff's Neurology in Clinical Practice, Treatment of Wernicke Encephalopathy
• Robbins & Kumar Basic Pathology, Thiamine Deficiency
• Creasy & Resnik's Maternal-Fetal Medicine, Nutritional Neuropathies
• Rosen's Emergency Medicine, Hyperemesis Gravidarum
• Yamada's Textbook of Gastroenterology, Nausea and Vomiting of Pregnancy

Long-Term Fetal Neurodevelopmental Effects of Untreated Wernicke's Encephalopathy in Pregnancy

1. Direct thiamine deficiency in the fetus (from untreated maternal WE)
2. General effects of severe maternal HG/malnutrition on fetal brain development
3. Secondary fetal complications (prematurity, growth restriction, hemorrhage)

1. Fetal Thiamine Deficiency — Direct Effects

• Oxidative glucose metabolism in neurons
• Myelin synthesis
• Nucleic acid (pentose phosphate pathway) and neurotransmitter synthesis

Neonatal/infantile thiamine deficiency (resulting from maternal depletion):

• Infantile Wernicke's encephalopathy — reported in breastfed infants of severely thiamine-deficient mothers; presents with ocular signs, hypotonia, seizures, and cardiac failure
• Leigh syndrome-like metabolic encephalopathy — in severe postnatal thiamine deficiency
• Brainstem dysfunction — feeding difficulties, respiratory irregularity

2. Structural Brain Effects — Evidence from HG-Exposed Children

"Our systematic review showed that maternal hyperemesis gravidarum is associated with small increases in adverse health outcomes among children, including neurodevelopmental disorders, mental health disorders, and possibly testicular cancer." — Nijsten et al., 2022

• 50% increased risk of neurologic hospitalization (HR 1.50, 95% CI 1.32–1.71)
• 51% increased risk of developmental disorder hospitalization (HR 1.51, 95% CI 1.29–1.76) in children up to age 16

Bottom line on HG-associated neurodevelopmental risk: The signal is real in observational data, but confounding is substantial. A direct causal pathway — likely mediated by thiamine and other micronutrient deficiency — plausibly exists but is difficult to isolate.

3. Secondary Fetal Complications of Untreated HG/WE

Growth and Prematurity

• Low birthweight (LBW) and small for gestational age (SGA) — from poor maternal weight gain (<7 kg in pregnancy)
• Preterm birth — associated with cerebral palsy, intraventricular hemorrhage, white matter injury, and long-term cognitive impairment
• Poor 5-minute Apgar scores — marker of perinatal asphyxia

"Maternal malnutrition during pregnancy often results in prematurity and other obstetrical complications... Premature infants and infants with low birth weight are at high risk for neurologic and subtle intellectual impairments that may not be apparent until their school years." — Kaplan & Sadock's Synopsis of Psychiatry

"Among children with low birth weight (<1 kg), 20% had significant disabilities including cerebral palsy, intellectual disability, autism, and severe learning problems." — Kaplan & Sadock's

Fetal Intracranial Hemorrhage (Vitamin K Deficiency)

• Prolonged HG → Vitamin K deficiency → fetal coagulopathy
• Third-trimester fetal intracranial hemorrhage has been reported
• Perinatal intracranial hemorrhage → periventricular white matter injury → cerebral palsy, cognitive impairment, epilepsy

"Congenital malformations are more common, and fetal coagulopathy and chondrodysplasia have been reported from vitamin K deficiency, with third-trimester fetal intracranial hemorrhage." — Yamada's Textbook of Gastroenterology

Fetal Demise

• Stillbirth/fetal demise has been reported in untreated severe WE during pregnancy (including in Wernicke-Korsakoff syndrome case reports in the Goldman-Cecil reference database)

4. Why the First Trimester Is Particularly Vulnerable

• Neurulation (weeks 3–4) — neural tube closure
• Neuronal proliferation (weeks 6–18) — peak cell division
• Cortical organization begins — disruption here can produce structural changes (as seen in cortical volume studies above)

Summary of Fetal/Neonatal Risks from Untreated Maternal WE in Pregnancy

Clinical Implication

• Yamada's Textbook of Gastroenterology, 7th ed., Outcome section
• Kaplan & Sadock's Synopsis of Psychiatry, Complications of Pregnancy
• Nijsten et al. (2022), Am J Obstet Gynecol [PMID 35367190] — Systematic review & meta-analysis
• Auger et al. (2024), Eur J Pediatr [PMID 38884821] — Longitudinal cohort, 1.2M children
• Pont et al. (2025), Am J Obstet Gynecol [PMID 40064411] — Sibling-design cohort, 700K children

Differential Diagnoses: Nystagmus + Vomiting in First Trimester Pregnancy

1. What is causing the nystagmus?
2. Is the vomiting causally related to the nystagmus, or are they independent?

Differentials — Ranked by Likelihood

⭐ 1. Wernicke Encephalopathy (Most Likely — Must Not Miss)

• Mechanism: Thiamine (B1) deficiency from prolonged vomiting
• Key features: Nystagmus (horizontal > vertical), ophthalmoplegia, ataxia, confusion — often incomplete triad
• Vomiting: Causally linked — HG depletes thiamine → WE
• Why it tops the list: Treatable and reversible if caught early; irreversible if missed
• Red flag: If glucose is given IV without thiamine first, WE is precipitated or worsened

2. Posterior Circulation Stroke / Cerebellar/Brainstem Infarction

• Mechanism: Vertebrobasilar ischemia — cerebellum or brainstem
• Key features: Acute onset, nausea/vomiting, nystagmus, ataxia, possible diplopia, dysphagia, facial numbness, Horner syndrome
• Nystagmus pattern: Direction-changing or purely vertical → strongly suggests central lesion
• HINTS exam at bedside differentiates central from peripheral:
  • Head Impulse (normal = bad sign → central)
  • Intermediate direction-changing Nystagmus (present = central)
  • Test of Skew (vertical skew deviation = central)
• Note: Pregnancy is a hypercoagulable state, increasing stroke risk (though more so in 2nd/3rd trimester)
• Imaging: MRI brain with DWI (CT has low sensitivity for posterior fossa)

3. Multiple Sclerosis — Demyelinating Episode

• Mechanism: Demyelinating plaque in brainstem/cerebellum (MLF → internuclear ophthalmoplegia; vestibular nuclei → nystagmus)
• Key features: Young woman, relapsing symptoms, INO (dissociated nystagmus on lateral gaze), Uhthoff phenomenon
• Note: MS relapses typically decrease in first trimester and increase postpartum — but first presentation in pregnancy is possible
• Nystagmus pattern: INO produces ataxic nystagmus in the abducting eye; pendular nystagmus with visual loss possible
• Imaging: MRI brain/spine with gadolinium (avoid gadolinium in first trimester if possible)

4. Vestibular Neuritis / Labyrinthitis

• Mechanism: Viral inflammation of vestibular nerve (CN VIII) or labyrinth
• Key features: Acute severe vertigo, nausea/vomiting, horizontal-rotary nystagmus with fast phase away from affected ear, positive head impulse test (peripheral pattern), NO hearing loss (neuritis) vs. WITH hearing loss/tinnitus (labyrinthitis)
• Key distinction from central: Nystagmus is unidirectional, fatigable, suppressed by fixation; head impulse test is positive; no other neurological signs
• Note: Vomiting here is driven by the vestibular disorder, not HG — needs to be separated clinically

5. BPPV (Benign Paroxysmal Positional Vertigo)

• Mechanism: Canalith displacement in semicircular canals
• Key features: Brief (seconds), triggered by head position change, upbeat-torsional nystagmus on Dix-Hallpike
• Vomiting: Mild; not the severe starvation-level vomiting of HG
• Important caveat: Dix-Hallpike should be avoided in patients with acute vestibular syndrome (constant nystagmus + vomiting) until posterior fossa stroke is excluded — a positive Hallpike can be falsely reassuring

6. Posterior Fossa Mass / Tumor

• Mechanism: Cerebellar or brainstem tumor (e.g., medulloblastoma, ependymoma, acoustic neuroma, brainstem glioma)
• Key features: Subacute progressive course, downbeat or gaze-evoked nystagmus, ataxia, CN deficits
• Nystagmus types indicating structural posterior fossa lesion:
  • Downbeat nystagmus → cervicomedullary junction (Chiari malformation), cerebellar degeneration
  • Seesaw nystagmus → parasellar/chiasmal region (pituitary tumor)
  • Convergence-retraction → dorsal midbrain (pineal tumor, Parinaud syndrome)
  • Gaze-evoked → cerebellar/brainstem disease
• Imaging: MRI brain with contrast

7. Arnold-Chiari Malformation (Decompensation)

• Mechanism: Tonsillar herniation compressing cervicomedullary junction
• Key features: Downbeat or periodic alternating nystagmus, occipital headache worsened by Valsalva/coughing, ataxia
• Pregnancy relevance: Increased intracranial pressure in pregnancy can unmask or worsen a previously compensated Chiari I malformation

8. Drug/Toxin-Induced

• Mechanism: Antiemetic toxicity (e.g., metoclopramide → oculogyric crisis, not true nystagmus), carbamazepine, phenytoin, lithium, alcohol
• Nystagmus type: Gaze-evoked nystagmus is most commonly drug-induced (sedatives, anticonvulsants, alcohol)
• Consider medication history carefully

9. Metabolic Encephalopathies

• Hyponatremia (from prolonged vomiting, HG) — altered sensorium, seizures, possible nystagmus
• Hypoglycemia — especially if patient has reduced intake
• Both can complicate HG directly

Summary Table

Bedside Approach

1. Give IV thiamine (500 mg) immediately — before glucose, before MRI — if WE is clinically possible. The risk of treatment is negligible; the cost of missing WE is catastrophic.
2. HINTS exam — rules in/out central cause at bedside
3. MRI brain (FLAIR, DWI, T2) — single most important investigation; shows WE lesions, ischemia, demyelination, tumors
4. Electrolytes, glucose, thiamine level, serum B12 — metabolic screen
5. Medication review — antiemetics, other drugs

• Wills Eye Manual, Nystagmus with Localizing Neuroanatomic Significance
• Rosen's Emergency Medicine, Characteristics of Peripheral and Central Vertigo (Table 15.3)
• Bradley and Daroff's Neurology in Clinical Practice, Treatment of Wernicke Encephalopathy
• Harrison's Principles of Internal Medicine 22E, Acute Vestibular Syndrome / HINTS exam