Long Island Concussion
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Legal Analysis

What Is a Concussion and How Do Car Accidents Cause It?

A concussion is a traumatic brain injury caused by a biomechanical force that disrupts normal brain function. The term is now used interchangeably with mild traumatic brain injury (mTBI) in most clinical and forensic settings. Despite the word “mild,” the functional consequences of a concussion can be severe and prolonged — particularly when symptoms develop into post-concussion syndrome.

In a car accident, concussion most commonly results from one of two mechanisms. The first is direct impact — the head strikes the steering wheel, headrest, window, or door frame during the collision. The second, and often more legally complex, mechanism is rapid acceleration-deceleration without direct head impact. In a rear-end collision, the head whips forward and backward, causing the brain to move inside the skull. The brain strikes the interior of the skull on the side of initial movement (the coup injury) and then rebounds to strike the opposite side (the contrecoup injury). This coup-contrecoup pattern can cause diffuse injury across multiple brain regions.

At the cellular level, the critical injury mechanism is axonal shearing — the stretching and tearing of axons, the long projections of neurons that transmit signals across the brain. Axons are particularly vulnerable to the shear forces generated by rapid rotational acceleration of the brain during a crash. When axons shear, they lose the ability to transmit electrochemical signals efficiently. This disruption to the brain’s white matter communication pathways is what produces the cognitive symptoms of concussion: slowed processing speed, impaired working memory, difficulty concentrating, and executive function deficits. Critically, axonal shearing is invisible on standard MRI and CT — conventional imaging resolves macrostructural injury (bleeding, contusion, edema) but cannot detect the microstructural white matter disruption caused by axonal shearing.

Concussion symptoms typically include headache (the most common symptom), cognitive fog and slowed thinking, memory difficulty particularly for recent events, difficulty concentrating, dizziness and balance problems, nausea, sensitivity to light (photophobia) and sound (phonophobia), sleep disturbance, emotional changes including irritability and depression, and visual disturbances. Most concussions resolve within 7-14 days, but a significant subset of patients — estimates range from 10% to 30% — develop post-concussion syndrome, in which symptoms persist beyond three months and cause substantial functional impairment.

Traditional concussion grading scales (Grade 1, 2, 3 based on loss of consciousness and amnesia duration) are still used in clinical and litigation settings but are increasingly supplemented by functional assessment tools. Second impact syndrome, while rare, is legally significant: a second concussion sustained before the first has fully resolved can cause catastrophic or fatal cerebral edema. In litigation, evidence that a defendant’s negligence caused a second impact on a person still recovering from a prior concussion significantly elevates damages exposure.

Evidence sources for concussion causation include emergency room records documenting the mechanism of injury and initial symptoms, ambulance records noting loss of consciousness or confusion at the scene, eyewitness accounts of the victim’s behavior immediately after the crash, police report descriptions of the collision’s severity and the victim’s condition, athletic trainer reports if the victim participated in sports, and vehicle black box data establishing the force of impact. See also our car accident lawyer page for a full discussion of vehicle accident causation evidence.

Post-Concussion Syndrome: When Symptoms Don’t Go Away

Post-concussion syndrome (PCS) is defined by the persistence of concussion symptoms beyond the expected recovery period — generally recognized as more than three months after the initial injury. PCS is a recognized diagnostic entity under both ICD-10 (F07.81) and DSM-5, and its existence is supported by substantial peer-reviewed literature. In New York personal injury litigation, PCS is among the most powerful diagnoses for satisfying the serious injury threshold under Insurance Law §5102(d) because it transforms an injury that might otherwise appear transient into a documented chronic condition with measurable, objective functional impact.

The symptom profile of PCS typically includes persistent or recurrent headaches (often evolving into post-traumatic migraine disorder), cognitive fog and slowed processing speed, memory problems (particularly encoding and retrieval of new information), difficulty sustaining concentration, sleep disturbance (both hypersomnia and insomnia patterns), emotional lability including depression, irritability, and anxiety, light and sound sensitivity, dizziness and vestibular dysfunction, and visual processing difficulties. The constellation of symptoms varies by individual, but the characteristic pattern of PCS — cognitive, physical, and emotional symptoms simultaneously following a head injury — is clinically recognizable and legally documentable.

Neuropsychological testing is the cornerstone of PCS documentation for litigation purposes. A licensed neuropsychologist administers a standardized battery of validated tests measuring the specific cognitive domains affected by concussion: verbal and visual memory (encoding, consolidation, and retrieval), processing speed, working memory capacity, sustained attention and concentration, executive function (planning, cognitive flexibility, inhibition), and visuospatial processing. The neuropsychologist then compares the plaintiff’s performance on each measure to age- and education-matched normative data from large population samples. A score that falls more than one or two standard deviations below the normative mean represents a statistically significant deficit — objective evidence that the brain is not functioning normally. This data satisfies Toure v. Avis’s objective evidence requirement because it is measured by standardized instruments with published reliability and validity data, not simply the plaintiff’s subjective complaints.

The functional impact of PCS on employment is a critical damages component. A financial analyst who cannot process numerical data at normal speed, a teacher who cannot maintain a classroom, an attorney who cannot follow complex legal argument, or a tradesperson who cannot safely operate equipment due to dizziness and cognitive fog all face real vocational consequences from PCS. Vocational assessments, employer records of missed work and performance decline, and the treating neuropsychologist’s opinion on work capacity translate the test scores into concrete economic damages. For related functional impairment claims, see our page on PTSD and emotional distress, which frequently co-occurs with PCS following traumatic accidents.

Proving a Concussion Under §5102(d) When Imaging Is Normal

The central legal challenge in concussion litigation is satisfying the serious injury threshold under Insurance Law §5102(d) when standard MRI and CT scans are normal. Insurance carriers treat a normal MRI as the end of the conversation. It is not — but overcoming it requires a sophisticated evidentiary strategy.

The New York Court of Appeals established in Toure v. Avis Rent A Car (2002) that objective medical evidence is required to satisfy the threshold. However, the Court did not hold that positive MRI or CT findings are required. Objective evidence means evidence derived from medical examination, testing, or observation rather than the plaintiff’s unverified subjective complaints. Neuropsychological test scores derived from standardized instruments with published norms are paradigmatically objective. A DTI scan with abnormal fractional anisotropy values reported by a radiologist is objective imaging evidence. A vestibular therapist’s quantified balance and eye movement assessments are objective. These are the tools that substitute for positive MRI findings when the standard imaging is negative.

DTI (Diffusion Tensor Imaging) is increasingly central to concussion litigation in New York. DTI is an MRI protocol that measures the diffusion of water molecules along white matter tracts. In a healthy brain, water diffuses preferentially along the axon’s long axis, producing a measurable property called fractional anisotropy (FA). When axons are damaged by the shearing forces of concussion, the structural integrity of the white matter tract is disrupted, and FA values decrease. DTI can reveal abnormalities in frontal lobe tracts, the corpus callosum, and other white matter pathways that standard MRI completely misses. A radiologist’s report documenting significantly reduced FA in frontal or temporal white matter tracts, correlated with neuropsychological deficits in the cognitive domains served by those tracts, constitutes powerful objective evidence of organic brain injury.

ImPACT testing (Immediate Post-concussion Assessment and Cognitive Testing) provides a before-and-after comparison when a pre-injury baseline exists. Many high school and college athletes take baseline ImPACT tests at the start of each season. A student athlete who sustains a concussion in a car accident can compare their post-injury ImPACT scores against their own pre-injury baseline, objectively documenting the decline in processing speed, reaction time, and memory function caused by the injury. For plaintiffs without a pre-injury baseline, normative comparison data from population studies can substitute.

The threshold categories most commonly satisfied in concussion cases with normal standard MRI are: (1) the significant limitation category, when neuropsychological testing and functional assessment document a meaningful restriction on daily activities or work capacity that is more than minor; and (2) the 90/180-day category, when the plaintiff demonstrates through employer records and treating physician affidavits that they were unable to perform substantially all of their customary daily activities for more than 90 of the first 180 days following the accident. In severe PCS cases with permanent documented cognitive deficits, the permanent consequential limitation category may also apply. For a full discussion of serious injury threshold categories, see our car accident lawyer page. For moderate and severe TBI with positive imaging findings, see our brain injury attorney page.

Children, Concussions, and the Infant Statute of Limitations Toll

Children and adolescents are particularly vulnerable to concussion and its long-term consequences. The developing brain is more susceptible to the effects of axonal shearing, and recovery from concussion in pediatric patients is often longer and more complicated than in adults. Children who sustain concussions in car accidents face unique medical and legal considerations that demand specialized handling.

The most important procedural distinction for pediatric concussion claims is the CPLR §208 infant toll. Under this statute, the statute of limitations for a personal injury claim is tolled — suspended — during the period of a plaintiff’s infancy. In New York, “infancy” for CPLR purposes means being under age 18. A child who is injured in a car accident at age 10 does not face the standard 3-year statute of limitations under CPLR §214 expiring when the child is 13. Instead, the toll applies until the child turns 18, at which point the 3-year statute of limitations begins to run — giving the injured child until age 21 to file suit.

This toll is significant because children’s post-concussion symptoms may not be fully recognized or evaluated until years after the injury. A child who develops academic difficulties, behavioral changes, or emotional symptoms following a car accident may not receive a formal neuropsychological evaluation connecting those symptoms to the concussion for years. The infant toll preserves the claim during the period when the full consequences of the injury are still developing and being recognized.

School records are a uniquely valuable evidence source in pediatric concussion cases. Pre-injury and post-injury grade reports, teacher observations, attendance records, and any records of academic accommodations (504 plans, IEP modifications) document the cognitive functional impact of the concussion on the child’s educational performance. School nurses’ records of complaints and return-to-learn protocols provide contemporaneous documentation of symptom duration. Athletic trainer records and return-to-play assessments, which schools are required to maintain under New York Education Law for student athletes, document both the concussion event itself and the recovery timeline.

Pediatric neuropsychological evaluation requires a specialist experienced with pediatric cognitive norms — the population comparisons used for adult neuropsychological testing are not appropriate for developing brains. A pediatric neuropsychologist administers age-appropriate instruments and compares the child’s performance to peer-age normative data, identifying deficits that are significant relative to what is expected for a child of that age and developmental stage. This evaluation, combined with school records and the treating pediatric neurologist’s opinion, forms the foundation of a pediatric concussion claim.

How Insurers Attack Concussion Claims and How We Respond

Insurance carriers defending concussion claims deploy a predictable set of arguments designed to minimize or eliminate the claim. Understanding these arguments — and the evidence that defeats them — is essential to building a concussion case that survives summary judgment and achieves fair value at settlement or trial.

The pre-existing anxiety/depression defense is the most common attack on post-concussion syndrome claims. Because PCS symptoms include mood changes, anxiety, and depression, and because anxiety and depression are common in the general population, defense IME neuropsychologists routinely argue that the plaintiff’s cognitive and emotional symptoms reflect a pre-existing psychiatric condition rather than a brain injury from the accident. The response requires a thorough pre-accident medical and psychiatric history review. If the plaintiff had no documented anxiety, depression, or cognitive complaints before the accident, the temporal relationship between the crash and the onset of symptoms is powerful evidence of causation. Even where pre-existing conditions exist, New York’s eggshell plaintiff rule holds the defendant liable for the aggravation of those conditions caused by the accident.

Malingering allegations are a specific defense tactic in cases with normal imaging and subjective symptoms. Defense neuropsychologists may administer symptom validity tests (SVTs) and performance validity tests (PVTs) during IME neuropsychological evaluations, then argue that scores below threshold indicate intentional exaggeration of deficits. The response is a comprehensive validity analysis conducted by the plaintiff’s own neuropsychologist, contextualizing SVT and PVT performance within the full neuropsychological battery and clinical presentation. Research demonstrates that genuine mTBI can produce performance patterns that superficially resemble exaggeration on some validity measures — context and clinical judgment matter. We prepare our expert witnesses specifically to address malingering allegations.

The low-speed impact defense argues that the collision’s velocity was insufficient to cause brain injury. Defense biomechanical engineers calculate change-in-velocity (delta-v) and argue that forces below a threshold cannot produce concussion. The scientific literature does not support a firm speed-below-which-concussion-cannot-occur threshold. Concussion is produced by the rotational acceleration of the brain, which depends on the mass and geometry of the head, the direction of impact, and the restraint system — not simply the vehicle’s speed. A concussion can occur in a relatively low-speed collision if the head is not restrained or if the rotational forces are sufficient. We retain biomechanical and neurological experts to respond to low-speed defense arguments.

IME neuropsychologist opinions are a structural feature of concussion defense. Insurance carriers are entitled to schedule an independent medical examination of the plaintiff, and they routinely retain neuropsychologists who regularly testify for defense. These IME neuropsychologists review the plaintiff’s neuropsychological testing records and often argue that the deficits are mild, inconsistent, or attributable to non-neurological factors. The response requires a qualified plaintiff’s neuropsychologist who can testify credibly about the significance of the documented deficits and rebut the defense expert’s methodology. We work with neuropsychological experts experienced in concussion litigation specifically. For spinal injury claims that frequently accompany concussion in car accidents, see our spinal cord injury lawyer page.