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Top 24 Differential Diagnosis for a 14-year-old female, not pregnant, with typical or atypical symptoms of Blackouts, Dizziness, Severe Aches And Pains, I Lost Language, Simply Forgetting How To Talk, Reading Became Impossible As Words And Letters Floated Around The Page, Disconnected, Joint Pain And Fatigue, Muscle Weakness Became So Severe That I Could No Longer Get Out Of Bed To Go To School, No Longer Walk Independently, Insomnia, Reflux, Vomiting And Extreme Sensitivity To Light And Sound

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adolescent female blackout language loss muscle weakness differential diagnosis

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14 year old female blackouts language loss aphasia muscle weakness joint pain photophobia dizziness differential diagnosis

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autoimmune encephalitis adolescent female aphasia seizure

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pediatric multiple sclerosis diagnosis

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myalgic encephalomyelitis chronic fatigue syndrome pediatric adolescent

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anti-NMDA receptor encephalitis adolescent female presentation language loss reading difficulty joint pain reflux insomnia

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Lyme neuroborreliosis pediatric encephalopathy cognitive

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juvenile systemic lupus erythematosus neuropsychiatric

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POTS dysautonomia Ehlers Danlos syndrome adolescent female blackouts cognitive dysfunction reading difficulty joint pain differential diagnosis

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Top 24 Differential Diagnoses

Patient: 14-year-old female, not pregnant Symptom complex: Blackouts/syncope, dizziness, severe diffuse pain, sudden language loss (expressive aphasia), visual distortion (letters/words floating), disconnection/dissociation, joint pain, profound fatigue, inability to walk or rise from bed, insomnia, reflux/vomiting, extreme photophobia and phonophobia
This is a complex, multi-system, neurological-autonomic-rheumatological presentation in an adolescent female. The combination of acute-onset language loss + cognitive symptoms + autonomic + musculoskeletal symptoms narrows the list considerably. Diagnoses are grouped by most likely first, with key distinguishing features.

Tier 1 - Highest Priority (Must Rule Out Urgently)

1. Anti-NMDA Receptor Autoimmune Encephalitis

Best fit for this presentation. The #1 most common autoimmune encephalitis and disproportionately affects adolescent and young adult females. Classic progression: flu-like prodrome → behavioral/psychiatric change → language loss/aphasia → seizures/blackouts → autonomic instability → movement disorder → decreased consciousness. Word-finding loss, speech regression, cognitive fragmentation (words "floating"), insomnia, and reflux from autonomic dysfunction are all documented features. In females aged 12-45, check for ovarian teratoma as a trigger.
  • Key test: CSF and serum anti-GluN1 (NMDA-R) antibodies; EEG, MRI brain
  • References: Goldman-Cecil Medicine; PMID 40355209 (2025 case series - adolescent with motor aphasia as first symptom)

2. Other Autoimmune Encephalitides

Related antibody-mediated encephalitides also affect young females and can present with overlapping features:
  • Anti-LGI1 (limbic encephalitis: memory loss, seizures, faciobrachial dystonic seizures)
  • Anti-CASPR2 (pain, autonomic instability, cognitive decline)
  • Anti-AMPA receptor (limbic symptoms, psychosis)
  • Anti-GABA-B receptor (seizures, behavioral change)
  • VGKC-complex antibodies
All require CSF antibody panel. Goldman-Cecil Medicine groups these as the three characteristic syndromes: limbic encephalitis, diffuse cortical encephalitis, and brainstem/cerebellar encephalitis.

3. Viral Encephalitis (HSV, EBV, HHV-6, CMV, Enterovirus)

Herpes simplex encephalitis (HSV-1) causes aphasia, behavioral change, and seizures from temporal lobe involvement. EBV (infectious mononucleosis) in adolescents can cause encephalitis, profound fatigue, joint pain, and occasionally cognitive symptoms. Post-HSV encephalitis can trigger secondary anti-NMDAR encephalitis weeks later. Requires urgent MRI brain and CSF PCR.

4. Juvenile-Onset Neuropsychiatric Systemic Lupus Erythematosus (jSLE)

SLE onset in the first two decades is more severe and more neurologically involved than adult SLE. Neuropsychiatric jSLE (NP-jSLE) includes: cognitive dysfunction, aphasia-like episodes (especially with antiphospholipid syndrome causing TIA/stroke), headache, seizures, psychosis, and extreme fatigue. Joint pain and photosensitivity are hallmarks. GI involvement (reflux, nausea) common. Female predominance is very strong.
  • Key tests: ANA, anti-dsDNA, complement (C3/C4), antiphospholipid antibodies, urinalysis
  • References: PMID 38061949; PMID 37556020

5. Multiple Sclerosis (Pediatric-Onset MS)

Pediatric MS accounts for ~5% of all MS cases and has a female predominance. Demyelinating attacks can cause transient aphasia, visual disturbances (oscillopsia - letters appearing to move), optic neuritis causing visual distortion, limb weakness, extreme fatigue, and Lhermitte's sign. Relapsing-remitting pattern with episodes of disconnection and neurological fog. The 2024 revised McDonald criteria now apply to pediatric cases.
  • Key test: MRI brain + spine with gadolinium, CSF oligoclonal bands, VEPs
  • References: PMID 40975101 - 2025 updated McDonald criteria

6. MOGAD (Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease)

Distinct from MS, MOGAD is an inflammatory CNS demyelinating disorder now recognized with its own diagnostic criteria (Banwell et al., Lancet Neurology 2023 - PMID 36706773). It presents with optic neuritis (visual disturbance), ADEM-like episodes, transverse myelitis, and cortical encephalitis. Language disruption, cognitive fog, and fatigue are documented. Can present with extreme sensory sensitivity.

Tier 2 - Highly Probable Functional/Autonomic/Connective Tissue Disorders

7. POTS (Postural Orthostatic Tachycardia Syndrome) + Dysautonomia

POTS is the most common cause of blackouts and dizziness in adolescent females. When standing, inadequate cerebral perfusion causes: syncope, pre-syncope, brain fog, cognitive disruption, visual disturbance, extreme fatigue, insomnia, and GI dysmotility (reflux, vomiting). The cognitive symptoms can be severe enough to impair reading, language fluency, and school attendance. POTS is frequently comorbid with hEDS and ME/CFS.
  • Key test: 10-minute standing test or tilt-table test (HR increase ≥30 bpm)
  • References: PMID 34144933 - NIH Consensus, 2021

8. Hypermobile Ehlers-Danlos Syndrome (hEDS) / Hypermobility Spectrum Disorder (HSD)

hEDS is a heritable connective tissue disorder causing joint hypermobility, chronic joint pain, fatigue, and autonomic dysfunction. It is strongly co-morbid with POTS (found in ~31% of POTS patients). Dysautonomia from hEDS causes blackouts, dizziness, cognitive impairment, and GI issues (reflux, gastroparesis). Skin hyperextensibility and joint instability are clinical hallmarks. Many adolescent girls with this triad (POTS + hEDS + ME/CFS) remain undiagnosed for years.
  • Key test: Beighton score, skin extensibility, family history; exclude other EDS subtypes with collagen/genetic testing

9. ME/CFS (Myalgic Encephalomyelitis / Chronic Fatigue Syndrome)

ME/CFS in adolescents causes profound disabling fatigue, post-exertional malaise (worsening after any activity), cognitive dysfunction ("brain fog" including word-finding failure and reading difficulty), unrefreshing sleep/insomnia, widespread pain, orthostatic intolerance, and sensory hypersensitivity (photophobia, phonophobia). The inability to walk or leave bed is characteristic of severe ME/CFS. School absence and bedbound state are common presenting features.
  • Key diagnostic criteria: Canadian Consensus Criteria or IOM 2015 criteria
  • References: PMID 37742748 - 2023 Charité state-of-science review

10. Long COVID / Post-Acute Sequelae of SARS-CoV-2 (PASC)

Pediatric Long COVID can cause a syndrome nearly identical to ME/CFS: extreme fatigue, cognitive dysfunction (brain fog, word-finding loss, reading difficulty), POTS, joint pain, photophobia, phonophobia, insomnia, GI dysmotility (reflux), and the inability to attend school. Prevalence in children post-COVID is significant. Ask about COVID-19 history or serology.
  • References: PMID 38279014 - 2024 Eur J Pediatr review on pediatric Long COVID

Tier 3 - Neurological and Epileptic Disorders

11. Migraine with Aura (including Hemiplegic Migraine and Alice in Wonderland Syndrome)

Migraine in adolescents can cause: aphasia/dysphasia aura (language disruption lasting minutes-hours), visual auras with distorted letter perception (metamorphopsia, visual snow), severe photophobia and phonophobia, dizziness, vomiting, and profound post-ictal fatigue/weakness. Alice in Wonderland Syndrome - associated with migraine - causes exactly the experience of letters/words moving, distorted sizes, and disconnection. Hemiplegic migraine causes limb weakness mimicking stroke. Basilar migraine causes vertigo, syncope, and language disturbance.

12. Focal Epilepsy (Temporal/Frontal Lobe) with Post-Ictal Phenomena

Focal seizures arising from the language-dominant hemisphere can cause ictal aphasia (sudden inability to speak or understand language during seizure) and post-ictal weakness (Todd's paralysis). The blackouts may represent focal-to-bilateral tonic-clonic seizures. Temporal lobe seizures also cause dissociation ("disconnected" feeling), derealization, and autonomic symptoms (nausea, vomiting). An adolescent who "simply forgot how to talk" mid-episode is a red flag for seizure.
  • Key test: EEG (including sleep and prolonged), MRI brain

13. Rasmussen Encephalitis

Rasmussen's is a rare, progressive, unilateral hemispheric inflammatory condition affecting children and adolescents. It causes progressive focal epilepsy, aphasia (if dominant hemisphere), hemiplegia, and cognitive decline. Insidious onset, progressively worsening. Anti-NMDAR encephalitis can mimic Rasmussen on imaging.

14. Transient Ischemic Attacks (TIA) / Cerebrovascular Disease

In adolescents, TIAs can result from: antiphospholipid syndrome (especially with SLE), vasculitis, prothrombotic states, or paradoxical embolism (PFO). Transient aphasia + visual symptoms + limb weakness = classic TIA territory-specific symptoms. Rare but must be excluded urgently, particularly if associated with SLE or coagulopathy.
  • Key tests: MRI DWI (stroke protocol), echo, hypercoagulable screen

Tier 4 - Infectious and Inflammatory

15. Lyme Neuroborreliosis

Lyme disease (Borrelia burgdorferi) can cause encephalopathy, cognitive dysfunction, peripheral neuropathy, joint pain (arthritis), and fatigue. Neurological Lyme ("neuroborreliosis") causes foggy thinking, word retrieval problems, sleep disruption, and mood changes. In endemic areas, this is a top differential for a teenager with multi-system symptoms. Often misses the rash stage.
  • Key tests: Lyme ELISA + Western blot; CSF if neurological
  • References: PMID 41195425 - 2025 European neurology guidelines

16. Infectious Mononucleosis (EBV) with Neurological Complications

EBV mononucleosis in adolescents causes profound fatigue, myalgia, joint pain, and, in ~1% of cases, neurological involvement including encephalitis, cognitive symptoms, and rarely aphasia. Post-mononucleosis syndrome can persist for months with ME/CFS-like features. Ask about preceding sore throat, lymphadenopathy.
  • Key tests: Monospot, EBV serology (VCA-IgM/IgG, EA, EBNA)
  • References: PMID 37526456 - 2024 review

17. Autoimmune/Hashimoto Encephalopathy (SREAT)

Steroid-Responsive Encephalopathy Associated with Autoimmune Thyroiditis (Hashimoto's) causes: cognitive decline, aphasia-like episodes, myoclonus, seizures, behavioral changes, and extreme fatigue in adolescents. Often presents with high anti-TPO or anti-thyroglobulin antibodies. Thyroid function can be normal. Responds dramatically to steroids.
  • Key tests: TSH, free T4, anti-TPO, anti-thyroglobulin; CSF

Tier 5 - Metabolic and Endocrine

18. Mitochondrial Disease (e.g., MELAS)

Mitochondrial Encephalomyopathy with Lactic Acidosis and Stroke-like Episodes (MELAS) can present in adolescence with: stroke-like episodes causing aphasia and visual disturbance, headache, seizures, muscle weakness, exercise intolerance, and fatigue. The stroke-like episodes do not follow vascular territories. GI dysmotility is common. A 14-year-old with recurrent episodes of language loss + weakness + visual symptoms should raise this possibility.
  • Key tests: Serum/CSF lactate and pyruvate, MRI (characteristic cortical changes), mtDNA analysis

19. Addison's Disease (Primary Adrenal Insufficiency)

Adrenal insufficiency causes: profound weakness, fatigue, inability to function, postural hypotension (blackouts, dizziness), joint/muscle aches, nausea, vomiting, and salt craving. An adrenal crisis can mimic an acute neurological emergency. The combination of orthostatic symptoms, muscle weakness, and GI symptoms in an adolescent girl warrants screening.
  • Key tests: 8 AM serum cortisol, ACTH stimulation test, plasma ACTH

20. Hypothyroidism (Severe/Hashimoto's)

Severe hypothyroidism causes fatigue, cognitive slowing (which can manifest as word-finding difficulty and reading impairment), muscle weakness, joint pain, reflux, and hypersomnia/sleep disturbance. Hashimoto's thyroiditis is common in adolescent females and can fluctuate, causing both hypo- and hyperthyroid episodes.
  • Key tests: TSH, free T4, anti-TPO

21. Vitamin Deficiencies (B12, Thiamine, Vitamin D)

  • B12 deficiency: causes subacute combined degeneration of the cord (weakness, sensory loss), cognitive decline, and fatigue
  • Thiamine (B1) deficiency: can cause Wernicke's encephalopathy with confusion, visual disturbance, and ataxia even in adolescents with restricted diet
  • Severe Vitamin D deficiency: contributes to muscle weakness, bone pain, and fatigue

Tier 6 - Functional and Psychiatric (Diagnoses of Exclusion)

22. Functional Neurological Disorder (FND)

FND can produce: non-epileptic blackouts (dissociative seizures), functional weakness (inability to walk), functional movement disorders, cognitive symptoms (functional cognitive disorder), sensory hypersensitivity, and conversion-type aphasia. FND is a genuine neurological condition, not "faking." It is more common in adolescent females. However, FND must only be considered after organic causes are rigorously excluded, especially given the severity and breadth of this presentation.
  • Key tests: Video EEG (to characterize blackouts), Hoover sign, neuropsychological assessment

23. Fibromyalgia / Central Sensitization Syndrome

Fibromyalgia in adolescents causes diffuse musculoskeletal pain, extreme fatigue, non-restorative sleep, cognitive dysfunction ("fibro fog" including word-finding), photophobia, phonophobia, and GI symptoms (IBS, reflux). Central sensitization amplifies all sensory inputs. Often co-exists with POTS and hEDS in adolescent females.

24. Anxiety / Panic Disorder with Somatic Amplification / Derealization Disorder

Severe panic attacks and anxiety can produce: blackouts (hyperventilation syncope), derealization/depersonalization ("disconnected"), visual disturbances, sensory hypersensitivity, and physical inability to function. Chronic anxiety causes muscular fatigue, insomnia, and GI symptoms. However, the aphasia and structural reading difficulty in this patient are unlikely to be purely anxiety-driven and suggest an organic neurological process that must be excluded first.

Summary Priority Matrix

PriorityDiagnosisMost Distinguishing Test
1Anti-NMDAR EncephalitisCSF anti-GluN1 antibodies, pelvic MRI
2Other Autoimmune EncephalitidesFull antibody CSF panel
3Viral Encephalitis (HSV/EBV)CSF PCR, MRI
4jSLE / NP-jSLEANA, anti-dsDNA, complement
5Pediatric MSMRI brain + spine, OCBs
6MOGADAnti-MOG antibodies
7POTS / DysautonomiaTilt-table / standing test
8hEDS / HSDBeighton score, clinical
9ME/CFSClinical criteria (exclusion)
10Long COVID / PASCHistory + serology
11Migraine with Aura (Hemiplegic/Basilar)Clinical, MRI to exclude
12Focal EpilepsyEEG, MRI
13Rasmussen EncephalitisMRI, EEG, CSF
14TIA / CerebrovascularMRI DWI, echo, hypercoag screen
15Lyme NeuroborreliosisLyme ELISA/Western blot
16EBV / Mono + neurologicalEBV serology, monospot
17Hashimoto Encephalopathy (SREAT)Anti-TPO, anti-TG, CSF
18Mitochondrial Disease (MELAS)Lactate, mtDNA, MRI
19Addison's Disease8AM cortisol, ACTH stim
20HypothyroidismTSH, free T4, anti-TPO
21Vitamin Deficiencies (B12/D/B1)Serum levels
22Functional Neurological DisorderVideo EEG, clinical criteria
23Fibromyalgia / Central SensitizationClinical (exclusion)
24Anxiety / Panic / DerealizationClinical (exclusion)

Clinical Bottom Line

The combination of acute aphasia + visual perceptual disturbance + blackouts + autonomic symptoms + severe debility in a 14-year-old girl is a neurological emergency until proven otherwise. Anti-NMDAR autoimmune encephalitis is the single most important diagnosis to exclude - it is the most common autoimmune encephalitis, predominantly affects adolescent females, and is treatable. The POTS/hEDS/ME/CFS triad is the next most likely cluster, as these three conditions are strongly co-occurring in this demographic and produce nearly the full symptom picture including the cognitive and language symptoms. jSLE and MS must also be excluded early with targeted blood and imaging workup.
This child requires urgent inpatient neurological evaluation with MRI brain + spine, lumbar puncture with full autoimmune antibody panel, EEG, and a comprehensive autoimmune and metabolic bloodwork panel.
Disclaimer: This information is for educational purposes. It does not replace assessment by a qualified clinician. A patient with this presentation requires urgent medical evaluation.
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